1. That's weak. So if an action has consequences and that action is banned, there is definitely logic to banning that action? And don't say I'm putting words in your mouth because that is exactly what you just said.
2. He was punished severely for breaking a blatantly stupid code, yes. If a code says I can't drink soda with a straw, and I break that code, should I be punished? It's not about following rules and regulations; it's about whether or not those rules and regulations are justified.
3. Again, self-evident. There is nothing inherently wrong with premarital sex. On a purely biological level, premarital sex is no different than post-marital sex. And what is ethically wrong with it? Just because the puritanical prudes turn their noses up at it doesn't mean it's wrong. If I haven't said anything of substance, then you haven't either.
4. But there are Mormons who do practice polygamy! They may be in the minority, as you say, but there are thousands of them out there. It wouldn't be the first time that a religious group hasn't followed its text. Christians and Jews and Muslims who say they are devout frequently do things that their teachings explicitly tell them not to do. And the religious leaders are no exception.