This person advocates for the "human" rights of the undead, robots, monsters, and other inhuman creatures. They will argue against killing them and make a case that they're just misunderstood Reluctant Monsters, or no different from human at all (except for dead flesh and/or machine parts, etc). Where this gets interesting is that the monsters in question may or may not be good, evil, or mixed. If they're good then they will call this to the attention of The Hunter to try and stop them from committing a Van Helsing Hate Crime. In more idealistic stories they're instrumental in getting the angry villagers (or disdainful scientists) and misunderstood monster to reconcile... or causing the monster to rampage when Hulk's Cooldown Hug Corollary is invoked. However, the monster's may well be mostly or completely evil when not ravening mindless creatures, and their advocacy is horribly out of place. They might be trying to protect a zombie bit loved one by denying it, or the monster (when intelligent) has tricked them or bought them off with promises of wealth or conversion. In these later cases, they usually die at the hands of their "loved one".
Hello, Unknown Troper. You'll need to get known to lend a hand here.