Casual Racism Is Not My Spirit Animal - great article, and could be applied to any -ism.
"[Casually racist comments] don’t have the same shock value as walking up to a person of color and calling them a racial slur. It’s not like being stung; it’s like being slowly burned, by a heat so gradual you barely notice it’s happening. Participating in most of these more casual things in social situations is unlikely to result in anyone going into full-on rage mode all over you.
(Quite the opposite: If you point out casual racism on a regular basis, you’re going to get a lot of people whining that you’re too “politically correct,” which is not a phrase that actually means anything anymore, besides saying of its speaker, “I am nostalgic for a time when I could be as racist as I wanted and nobody bugged me about it and thus I would like you to just shut up now you dumb person with your stupid thinky brain thoughts trying to infiltrate the hostile and unmovable lump of granite I replaced my mind with.”) (Uh, I may be embellishing a bit, there.)"