I'm straight and would not consider having sex with any man I didn't want to be with. So just say no and report anyone who hassles you. how is this just a trans thing, it's an across the board thing.
Because lesbians had words (lesbian, homosexual woman) to label a fact about themselves, that they had no sexual attraction to the male body, which they were using both legally to define some rights, and socially to define their own boundaries, spaces and culture.
But those words have had their meanings changed and that changes all the things, legal and social, that rest on them.
So those lesbians who know themselves to be same sex attracted, despite nothing changing in themselves, find themselves to now be treated as people who don't currently fancy any male bodies but that could always change.
And although they know that not to be true about themselves, it's now treated as an act of hate to be honest about this fundamental fact about themselves, or to want any support, spaces and culture that acknowledge and support single sex attraction even though they used to have them.
Exactly the same way as if womanhood is redefined from a fact of the body to a state of mind, many people who were quite happily being women up to that point find that word name no longer describes them but are told it's an act of hatred to say so, or to do anything to preserve or recreate the single sex provisions they used to have.