I know it always feels like the mods must be against you when you get a moderation reply, but I'm moderately sure we're not doing that. There is probably some unconscious bias but given how much practice we have at staying neutral—e.g. making a point of moderating bad comments even if we agree with them—such bias is probably relatively subtle. We also have a lot of practice at reviewing our own decisions, since users aren't shy about pointing out what they feel was biased. In those cases the moderation calls are usually defensible. Also, if we were grossly biased, we'd get major pushback from the community, which is always on the lookout for moderator overreach. That doesn't happen very often.

The thing is, even if someone else was being unkind, you still have to follow the site guidelines in how you respond.