It is, only if you believe in catholicism, or many other sects of christianity. I don't understand why some gay people want to be a part of, or change, a club that doesn't want them.
I believe in equal legal status for gays in every respect because I believe that is the most important status when it comes to being a citizen. But some gays want to be recognized as married under a christian institution... why??? Do I want to get married under some sort of KKK institution? NO, because I don't stand for what they believe in. I can understand gays hating certain groups because they don't like them. Great, that makes sense. What doesn't make sense is trying to hijack a club that you don't want to be a part of.
Everyone has the right to their own beliefs. Some people are meat eaters and don't give a shit about any animals that aren't cutesy, ie pets. Some people hate others of different color. Some people hate others of different political affiliations. Some people hate others of different sexual orientation. These people all have rights to form a group based on their discrimination so long as they don't break the law (that crosses the line for me). Lets not hijack their right to hate though.