Incest is barred for genetic reasons, not for moral ones. Close relatives bearing children limit gene pools, create more likely conditions for a child to inherit rare diseases or recessive traits, and ocaisionally results in genetic mutation/deformities. If you aren't planning on conceiving children naturally with someone who is a close blood relative, I doubt anyone could find a good reason NOT to support your decision to be with them anyway. And by GOOD reason, I mean a concrete scientific or moral reason.
"It gives me the willies" doesn't really count.
Chances are, we're all the product of quite a bit of incest somewhere down the line. ESPECIALLY if you're a believer of Judeo-Christian religions.