Plato, of course. Now, are we talking about homosexuality in Sparta or homosexuality in Greece as a whole. Maybe we need another separate topic for this? Also it is important to notice homosexuality does not appear either in art or literature before Classical time, even late Classical time. Labeling societies, some of which, like Sparta ended their glorious history somewhere in this period, on account of some practice geographically or socially far away is devastating to history...I can just imagine what would some men 2000 years from now think about our sexual practices, will US and Brazil be labeled as nations in which homosexuality is encouraged and all men love boys, or other men? There is certainly a great deal of evidence pointing to it(by the same twisted logics that puts institutionalized pederasty in Sparta, of all the poleis). Can we make that kind of conclusion then if we can label Spartans INDIRECTLY(using practices of other parts of Greece), and only from bad translation of two simple words...
I have a great example of this in my own language. We have a few centuries old song that says ''The boy, Lazarus, was scolded by his mother''
The exact same word for ''scold'' is used as a very common slang for sex or better say act of giving sex to someone, literary f******. In fact is is the most common term today, alongside polite one used by females which is ''sleeping with''.
I can only imagine some German or British (most common ones in Greek case) scholar coming here saying it was normal in our society for mothers to engage in sex with their sons

We would laugh to that.
The same happened with Greeks. History-or at least a version of narration- can be used to promote an agenda.
But let's stick to Sparta. Sparta had no single homosexual representation in either art or poetry. Not one. While there were many that were heterosexual representations. Also by understanding the Sparta system you will find out how hard it would actually be to be homosexual there, let alone encouraged to be like that, as if someone could make you...
With understanding the erastis and eromenoi words in Greek, and their meaning, foundation on homosexuality in Sparta ceases to exist. I am of course not saying there were never homosexual cases in Sparta (
to be more exact and correct myself we are not talking about adult male homosexuality which almost never appears in Greece, and when it does it is punished, but paedophilia so I am not sure why homosexuals even defend this mirrage), there always is, in every society, even parents misuse their children for sex.
But the practice was not only frowned upon but forbidden in Sparta. (no doubt it happened on separate occasions)
Erastis & Eromenos (Lover and Beloved or Inspirer and Listener(why does this have to be homosexual I don't understand - remember they were no English so other languages have words in different meanings)) were not of physical nature and when they were it was considered immoral most of the times. All who have read ancient texts notice the use of Erastis & Eromenos sometimes as a good thing but when physical love is involved it is of an immoral nature.From my readings i have understood that it was a composite issue and view.
The Erastis/eromenos bond remained important later in life (don't know where do you come from but in Medditeranean godfathers are very important in our life, and that originated from erastis and eromenoi relationship), and the fact that it does is evidence that it was far more and other than sexual bond. One of my favorite instances of twisting evidence to match preconceptions or agenda is the citing of a tale about a Spartan warrior who died fighting over his Erastes rather than let his body be taken. As if there is no bond between men that is worth dying over unless it involves genital insertion! On the contrary, as proved numerous times in history..I myself would fight far worse if the loved one was endangered as well. And then another where Agiselaos' son would not seek preference for a friend with out getting sex in return.
That Agiselaos (look at the date of this tale) spends much of his time fighting the urge to play with Persian youths is unreliable evidence for what happened at home. As I said, pedophiles did exist, hence the laws against them in Sparta.
I also enjoy the fact that scholars have taken the fact that anal intercourse was known colloquially in CLASSICAL Athens as "Laconian style" as evidence for homosexuality. Perhaps modern scholars are unaware that you can do this with a woman too!

In a culture where women marry at a comparatively late age, economic pressures push to small family size, and birth control options are limited, this becomes an important option.

Girls in many societies today do that for the same reason.
We have more evidence for Spartan sexuality from primary sources than we do for the mechanics of hoplite combat, yet so often this is ignored and anecdotes or analogies are strung together in their place. I'll let the ancients speak:
Xenophon is quite clear, though so often dismissed, is clear when he
states (Constitution of the Lakedaimonians.2.1):
[12] I think I ought to say something also about intimacy with boys,
since this matter also has a bearing on education. In other Greek
states, for instance among the Boeotians, man and boy live together,
like married people; elsewhere, among the Eleians, for example,
consent is won by means of favors. Some, on the other hand, entirely
forbid suitors to talk with boys. [13] The customs instituted by
Lycurgus were opposed to all of these. If someone, being himself an
honest man, admired a boy's soul and tried to make of him an ideal
friend without reproach and to associate with him, he approved, and
believed in the excellence of this kind of training.
But if it was
clear that the attraction lay in the boy's outward beauty, he banned
the connexion as an abomination; and thus he caused lovers to abstain
from boys no less than parents abstain from sexual intercourse with
their children and brothers and sisters with each other. [14] I am
not surprised, however, that people refuse to believe this. For in
many states the laws are not opposed to the indulgence of these
appetites.
Aristotle specifically addresses the homo eroticism of military
cultures and tells us Sparta is different from those who allow opened
homosexuality (and he is no apologist for Sparta as has been claimed
for Xenophon).
http://www.fordham.edu/halsall/ancient/aristotle- sparta.html
"the legislator wanted to make the whole state hardy and temperate,
and he has carried out his intention in the case of the men, but he
has neglected the women, who live in every sort of intemperance and
luxury. The consequence is that in such a state wealth is too highly
valued, especially if the citizens fall under the dominion of their
wives, after the manner of most warlike races, except the Celts and a
few others who openly approve of male loves. The old mythologer would
seem to have been right in uniting Ares and Aphrodite, for all
warlike races are prone to the love either of men or of women. This
was exemplified among the Spartans in the days of their greatness;
many things were managed by their women."
You really have to twist these quotes, or dismiss them, to render the meaning unclear. Sadly, true homosexuals in the modern sense of adult men involved in a romantic relationships were not free at all in ancient Greece to live openly that way. It is a shame that modern groups point to the greater acceptance of the physical use of men as a sexual outlet, but only if you were the "active" role, in the ancient world to bolster support for an emotional connection. Especially since the emotional tie, without sex, was much more accepted then.
Also key to the subject is understanding modern terminology.
Homoerotic is not homosexual, a point that seems lost on so many authors. When commercials market perfume to women by having half-naked female models parade around the screen they are tapping into homoerotic imagery. Women find the image attractive and erotic. They do not want to have sex with her...I myself was a Greeco Roman wrestler for decades, I studied at Faculty of Sports, we all admired well toned and buff pals, heck guys even compare and compete in their size...yet no one ever said there is any homosexuality among guys today even though they were naked and made comments or admired other male body.
This is important because the image of boys "at the age when they are most beautiful" would have been equally likely to have been used by an ancient Greek beer commercial as a pretty girl. They could assign eros equally.
There is a huge difference between saying that there was a homoerotic element to the link between "lovers" and assigning obligate intercourse.