Bigotry

Left unchecked and allowed the right environment and circumstances I believe that, at other points in history, the same kind of belief grew from something small and unchallenged to something that eventually attempted to exterminate those it marginalized. I know that's a dramatic leap to make as well as being a considerably offensive statement to those who disagree with me. We would all hope to be able to say that we are above actions like that. Still, I can't help being wary of humans. I know what they're like. I know that both the monumentally good and the incalculable evil always start growth as an innocuous looking seed.

[via Milestoned, emphasis mine]