"They look like monsters to you?"

[=AoD= Captain]

I'll still maintain that SH monsters were normal folks at one time. I believe Vincent, for whatever reason (long exposure to the environment, being a "monster" in his own right like Claudia) understands this idea or perceives more deeply into the creatures, recognizing a few perhaps for what they once were. Also monster is a loose term, some true monsters look perfectly acceptable. By saying they aren't monsters doesn't mean they appear as human to him, it just means that perhaps beyond the hideous exterior they are inwardly un-monstrous.