In anime culture, being normal is stupid, or something.
Seriously though, yeah. Just about every even vaguely normal human being on this planet is against incest on principle for a long list of very good reasons. The idea that it should be anything other than awful and incredibly, incredibly rare is beyond bizarre, and that is why it almost never shows up outside of anime culture: it shouldn't.
Seriously, the idea that being against incest is "silly"... :lol Oh anime culture, you can be so brain-hurtingly stupid sometimes.