I sometimes get confused, some of the people saying this are really young/children, others are probably just inexperienced.

Yes and no. There are young people in TRA circles, but a substantial portion of them are actual adults who believe in a fantasized version of what sex and relationships actually are.

Much of their vision about homosexuality is built around fiction, be it movies or anime, bacause as straight people they never had to experience what actually being gay or lesbian is first-hand.

The problem? Media tends to present a whitewashed version of what homossexuality actually is. I'm not even touching on the fetishists here, who also base their vision of the subject from media (be it porn or hentai/yaoi).

but have absorbed the social idea that lust/sex is hedonistic and bad, and really bad if that sex is gay (heavens forbid!).

I disagree with this mainly because like I said before: trans twitter is sex crazed, really sex crazed.

Their idealization of homossexuality also depends on stripping away what makes it actually a thing (materially speaking, of course) different from heterosexuality. In this context, being gay or lesbian becomes nothing more than a abstraction, no different from being straight. A dragon to be chased.

But they still know they want to feel loved, so you get the "hearts not parts" stuff.

This is a corruption of the original concept of platonic love: in it's original inception, carnal love (defined by physical sexuality) is one step towards platonic love, not an contradiction or something that can exist separate from it.

Something that most TRAs don't seem to understand is that a relationship cannot be born of only one side, or be sustained by fulfilling the needs of only one side. This is parasitism not love and will lead to a shitty life for both people involved.