Fiances sister and husband are both nuts?

Not only is she nuts, but so is his entire family.

Details:
-I'm 25 as is my fiance. We've been together for 6 years.

-His sister is 20 and got married at 18. Her husband is 24. She got engaged 4 months after knowing him and married the day after she got engaged. He's in the military and she doesn't work or go to college nor does she plan to. She didn't have a wedding, just went to a courthouse and got married there.

-They live in Texas and we live in New York.
Now, for the story. Get your popcorn ready!
They invited me to Texas a few mnths ago. It was rare for them to invite us considering she acts like I'm a parasite. We went out to eat at a decent restaurant. So we're eating while her husband is wearing a sleeveless shirt exposing his skull tattoos and all of a sudden, her husband burps loud. He says excuse me and laughs. 5 minutes pass..he does the same and she laughs too. At this point, I feel totally out of place and want to leave. I shake my head and they ask me what's wrong. I decline to answer. Then, without hesitation..he belches so loud that the guy behind out says ,"oh come on". He then stops and we leave.. I'm relieved.

Months pass and we invited them over. so now we're in new york at a slightly upper classed restaurant and he burps! then, he belches loudly and laughs as does she but while hes burping she tells him to stop while shes laughing. More time passes and he does it again and again and says"hold on, watch this" and he belches for 15 seconds straight.. I excuse myself and go to the bathroom being embarrassed.. My fiance joins me in the back of the restaurant and we decide that if he does it once more, we will tell him to stop.

So we get back and now its dessert time. He orders a sundae while we order cake. He's playing with his sundae by shaping it with his spoon like a snowman..He then drinks some soda, turns to his wife and belches in her ear. My fiance tells him to stop. Then, he does it again..So now I'm extremely embarrassed and I tell him to leave the restaurant. I literally said, "You need to grow up. Please leave now" He says I'm a bitch. So, I stand up and tell him "Do you want me to have the waiters assist you? LEAVE." At this point, I don't care that I'm making a scene. He tells me he'll stop burping if I sit down. I tell him to leave once more. He finally leaves as does his wife.

She's waiting outside with him. I get finished paying, go out and she has her hands on her hips. She tells me that was inappropriate and that I need to act more classy. I told her to grow up. Then, he mumbles something at me. I then say, "I don't have time for your immaturity. Why don't you go back to Texas to your free white trash apartment where you belong." They find a taxi..leave the state and she writes a nasty blog about me on her facebook page then deletes me after posting it.
Was this wrong of me? Is any of this normal?