I guess his whole argument is kind of moot because a character should be judge by their personality not by the Pokemon they use. It like saying Agatha likes killing people because she trains Ghost types, it's ridiculous.
P.S. While looking up Ghetsis's page I noticed this:
I haven't actually played W2 all the way through so I didn't know that this whole "he tried to kill the protagonist" thing, was actually a lie.In Pokémon Black 2 and White 2, Ghetsis is the first antagonist in the main series games to try to incapacitate the player. He attempts to have Kyurem freeze the player with Glaciate, but that move cannot cause freezing when used in battle. Before the English releases of Pokémon Black 2 and White 2, this threat was mistranslated by various sources as a threat to kill and impale them using Kyurem's icicles.