My issue isn't whether voting for a democratic candidate or not is better overall as a trans person, I think basically every trans person in the US knows that policy wise a democrat will, at worst, be the same as the republican they're running against on trans rights specifically, and at least a bit better on some others. (There is a consistent belief on every one of these posts that somehow trans people don't understand that as well, which is a different issue lol)

The point is that if a politician doesn't lose support/votes for taking an anti-trans position, then there's nothing punishing them for taking that position. That's the argument being made about how voting for an anti-trans democrat is voting against your own good, not because of their policy specifically, but because by voting for them in spite of it you send a signal that their position on trans issues can be the same as a republicans as long as they're marginally better than one in other ways.

For what its worth, I'm trans and am planning on voting for all Democrats in the midterms, even though I'm disappointed in a few of them. However, there are a couple candidates mentioned in this article specifically (namely cuellar + kaptur and a few others) where I think not voting for them has a very strong argument I'd consider if I lived in those states.