Snarks
Terrarian
There's also the fact that both the Crimson and Corruption come from Cthulhu (seeds from the EoC), and Cthulhu IS evil, so that would make them inherently evil as well.
Ah.
Maybe cthulhu in terraria is not evil? Have you ever thought of that? Maybe his story here is different.
Also why are you so sure they come from him? Does it say it somewhere in game? "Oh but it has the brain of cthulhu and eater of worlds!"
So what? The brain could have landed somewhere random and then started hiding that doesn't mean the biome is evil.
Also as far as I know the wall of flesh is also fleshy like crimson and I will use your "speculation" logic and I will construct my own theory saying that the wall of flesh
is a part of cthulhu and since it keeps not only the corruption and crimson at bay "from taking over the world" but it also keeps the death unicorns from eating your flesh. Oh but wait they are called unicorns which means they are the good guys... even though they pretty much want to kill you.
Anyways just because you speculate something doesn't mean it's right.