"Hey man it wasn't my sister... My sister's got a birthmark on her ass I'd know if it was her. No I haven't seen it she's told me about it."
Again, the denial issue. Just admit it, you are an inbred. You hate them because you are one. When you were young, everyone made fun of you for it, so now you feel like you have to make fun of inbreds and call everyone else one. It makes you feel better. Get over it, it isn't your fault, you were raised believing that it was right and everyone did it, then you found out that you were lied to (kind of like how Christians feel or maybe just Catholics).