I think it's because male Troons (especially AGP freaks) come across as more aggressively perverted, pushy, potentially violent, and just vile, they are men that chased a gross fetish so far down the rabbit hole they cut their dicks off and they take very obvious pleasure in shoving that perversion in peoples faces, whereas FtM Pooners, (ignoring the very gross and almost universal piss fetish) are mostly just pathetic, scared and broken little girls that seem to have huge body shame issues and an almost pathological fear of being raped and think they'll be safer if they disguise themselves as doods.
A manlet Pooner just isn't threatening, but a hulking 6'4" Hon is not only gross and disgusting but potentially threatening and dangerous.
It might very well be a double standard, but most people do find TiMs far more repulsive than Pooners, and less sympathetic.