This is all just my opinion.

As a goodie, you need a solid justification for killing other goodies. That will more often than not be role specific. Getting raided is generally considered plenty of justification for attacking another goodie and nobody would bat an eye, but I've also seen characters whose role would conflict with killing another goodie trying to retrieve. So, viewed through that prism, how good a reason does your character have for killing paladins? Azure? Good dwarves? etc...

I don't think it's a one size fits all rule works as well for a warden as, say, a Maran. There's also a whole lot of space for tense interaction between killing every paladin on sight and helping them run grab defiance.

Reavers are pretty much the flip side of the same analysis. Infighting is certainly allowed, and, at times, encouraged. But you still have common goals. If you're getting raided by a goodie conjie, for example, and you're fighting the reaver instead of the conjie, your character is a shitty outlander, even if it's totally IC and your character is good at having a gold aura.