but why warn for only transphobic slurs and not both?

A mistake, I thought that I already put it in and did not check.

Because the group tagged is more apt to assume it's in bad faith where as from personal experience being a bi fur most of my fur group has no issues calling each other that word but would probably not use it in a public setting like this

I personally find it kind of fun, especially on game chat if you hear someone using it as a slur to question them about why that's an insult and press them until they squirm

I'm not saying the word has not been used for harm but if you want that to end the only way forward is to change the accepted use of that and similar phrases