Because it's like, bad for the soul! It's demeaning and awful to let people use you that way! If it's done right, you know, with a husband or wife to be close with them, it's like, good and healthy and sacred, but it's not something you should throw around!

[Also, it reminds him of M!Pol, and Santana pisses him off with the Let's Scandalize Poland Game, so he's more vocal about it than he might otherwise be.]