Why is frowned upon that I date my cousin?

First off, I'm being serious here. I'm 16 and she's 12, and we're compatible. I don't care about how we're related, she is nice and sexy and I love her. We love each other and we use a condom okay? ANd if we have a baby we will abort it, so don't worry about mutants walking around okay we are responsible! I just don't get it, people say opposites attract but that'd a lot of hogwash hullabaloo. I'm gonna marry her and if that day comes when we wanna have a baby, I'll love that mutant so much and nurse it to death with care and happiness. I don't get, we're not hillbillies, we're from Texas! And there's not a lot to choose from, most of the girls that are into me are fat..