Vulgar Christians

I like to cuss. I like to cuss a lot. And I find it interesting, to observe who cusses with me, and who doesn't.
Last Christmas, my kind gay Christian friend shared a photo to Facebook of his husband wearing what he had given him: a warm fleece jacket with a small Oregon State University beavers logo.
In my part of southern Oregon, about half of the locals (by my estimate) support the University of Oregon ducks, and half support the Oregon State University beavers. Even the local dairy company puts out two different team-colored cartons of the same flavor of ice cream. (Unfortunately, it's like they're shitting on both teams, because all of their ice cream products are filled with corn syrup and taste disgustingly sweet, and I avoid them at all costs.)
Anyway, my friend bragged that "Rob loves his new jacket. We'll make a beaver fan out of him yet!"
I was so very tempted to make a dirty joke and blame it on autocorrect.
"I thought he liked dicks instead of beavers," I almost said, "Oh no, I mean DUCKS instead of beavers!"
And yet I didn't, because, though I knew that one of my other gay friends, an atheist, would probably howl with laughter, I didn't want to make my very proper Christian friend uncomfortable. So I settled for, "His smile says, 'I like the beavers now,' but his eyes say, 'Help me!'"
A few months later, I saw a picture of those two on a hike, and Rob was again wearing his warm Beaver pullover, though I'm guessing that he actually divorced his wife and married a man to get away from the beavers. I honestly don't know what his husband was thinking; they're already on the same team, anyway.
Interestingly enough, almost every gay Christian I know is very proper, never cussing or making dirty jokes; always going to church; and never being mean, even to the bigots and awful people. There was the one guy who said that he was a devout Christian, "and when I was born, I had to have a c-section, because I was so gay, I couldn't even come out of a vagina." (That's literally why we're now friends, in fact, because he said that.) But that's as vulgar as they come, at least in my circle of friends. 
The Christian straight allies, on the other hand, say things like, "I just love my lesbian daughter! I tell her all the time, 'I'm so glad I didn't swallow you!'" (It reminded me of my mom, but I didn't tell her that story, because I was afraid that I would hear that, too.) And, "I would draw a pentagram under the welcome mat for a demon trap, but I'm afraid my kids couldn't come in!" (This was said by the ultra-modest Christian who tried to help me start an atheist club at my school, in fact.)
There is a pansexual Christian I know who draws nudes (at least partly for aesthetic reasons), but I don't know if she counts. She seems like the kind to laugh at some dirty jokes, but is proper in other ways (anti-abortion, unlike the ultra-modest feminist woman I mentioned above).
I can see the LGBT Christians trying to prove to themselves and others that they're "real" Christians (if anyone can be called that), but I often wonder why, if they apparently reexamined and rejected one major item of their faith (since a lot of them come from conservative backgrounds--and to a gay person, this item is one of the biggest issues in religion), they don't just go all out and reexamine everything.
Why would God be opposed to "duck" jokes? Or, for that matter, premarital sex? (My own mom advises me to have premarital sex, if I ever have a boyfriend or girlfriend, rather than getting married because we want to have sex.) Why not cuss, if you're not using your words to hurt innocent people? Why be "holy" anyway? Or was the concept just made up by humans, in order to set themselves apart from others, so that they would have people to look down upon (or be able feel better about themselves morally)?
And why are the LGBT-affirming straight people I know so vulgar, even while being Christian? In this area, my proper gay Christian friends seem to have more in common with the homophobes--except that the gays are generally much nicer and therefore will only laugh politely, rather than giving you "sad" looks because you're "lost." The atheists and the straight Christians, meanwhile, will howl and giggle right alongside you.
I'm not sure exactly where I fit into all of this, though. I'm bisexual, so I'm both lesbian and straight. And I was a Christian, then an atheist, and now I often feel like both at the same time. But I'm definitely one of the vulgar ones. And I wouldn't have it any other way.