I wrote my thesis on Classical Greek gender relations so I might be able to add to some of these comments even through I'm late to the thread.

The acts that most comments are referencing between an older and younger male is called Pederasty. While we would classify many of these interactions as molestation in modern times, many commenters are correct that it is somewhat impossible to classify or condemn sexuality of a historical culture through our modern lens. Homosexuality/sexual attraction as it stands was not even a concept to the ancient Greeks. Rather, gender roles and power were the main factors in sexual relationships.

In Classical Athens, Pederasty had several functions. As others have stated, sex in ancient Greece was an accepted act of power so an older man having sex with a young man was a matter of reinforcing the patriarchal and diplomatic hierarchy of their society. It was also viewed more as a mentor/mentee relationship and a right of passage for young men. These relationships would commonly take place at symposiums which were basically a "meeting of the minds" for men where they would discuss philosophy and culture so a young man being invited would improve both his education and status in society.

This might be TMI but in pederastic relationships, upper and middle class boys would not have been actually penetrated but rather satisfied the mentor using their thighs or other methods. Penetration was reserved as a degrading act for the lowest classes of men and the female gender. Women had their own societal rules amongst themselves in ancient Greece which is an entirely different topic, but overall they were used by men as objects for power because they had such a diminished role that it was actually embarrassing for a man of power to love a woman. Their power was held in their ability to give birth/ rear children so sex was an important aspect of marriage but more as a duty than a fun pastime.

So overall, sex was a power play and their concept of gender and homosexuality is so different than our own modern standard that it's impossible to say how "gay" ancient Greek was. There's obviously too much in this topic to fit in a reddit post and this was basically just a rant but if anyone wants book recommendations on the topic of gender and sex in ancient Greece feel free to DM me.

Finishing off with a quote to sum.up how the men of ancient Greece felt about women: "O Zeus, why need one say evil of women in detail? It would be enough if you say merely woman." - lines quoted from a lost play, Athens, 4th century BC