The one who made that response is the lead dev of SerenityOS and presumably Ladybird as well, since he's the one who announced it.
Even if he didn't put that language in, he made the call that that language being in there was not political, but fixing it to be gender-neutral would be political.
I think the reason why it hits so hard is because it's an attack that lands under their own ideology. To them, being outside the normal is the worst thing you can be. They demonize everyone that they perceive as outside the normal. So, when they're accused of not being normal, they take that very seriously.
Most other attacks against them don't bother them as much since they're based in other ideologies and don't really land under their own ideology.