I’m going to go out on a limb and suggest they haven’t really looked into Spartan and ancient Greeks views on homosexuality…!
The whole thing I find quite bizarre anyway re using the Spartans as motivation - did they fall asleep before the end of the movie 300 and miss the bit where they all rather painfully died after being betrayed by a fellow Greek?
There is probably a very good book to be written on the psychological influence of
300 - certainly on reflection one could make a good argument that it influenced every superhero movie since as well as making audiences more receptive to that kind of thing. Loads of people lapped that film up.
In terms of their motivation, I'm sure they saw the end (indeed the end is the point) but historically it is mad that people living now picked up on them, almost to the exclusion of every other Greek city state. They were an abject failure even in Greek city-state terms by the 350s and had become a sort of live action ye-olde-times tourist attraction 400 years later.