Half of me supports gay marriage, the other half doesn't. Why?

Basically the title.

Years ago, I was so far right wing that there was no way I'd ever support "those fags" getting married, etc.

But now, being a few years older and a few years wiser (I'm early 20s), and getting to know more LGBT people I'm really trying my hardest to fully support this.

However, before I can fully convince myself that I do, there's a part of me that is still rejecting it and I can't figure out why.

That said, I have a few gay facebook friends who are more than open to sharing pictures of themselves kissing their partners. I actually am seriously grossed out when I see these pictures. Similarly, I REALLY want to like eating eggs but the texture and taste are just not something that I can handle.

Is this normal? Any thoughts as to what's blocking me from fully accepting this?

EDIT: Finding dudes kissing disgusting is NOT the thing keeping me from supporting it, so please don't reply with that thought. Conversely I think women kissing is hot as fuck, so there's something else that's preventing me from backing it.