Well, based on your posts in this thread, I would say that it's you that doesn't understand it. I haven't seen an 'evangelical' on here demanding that you believe what they believe. But, you have clearly stated on here that they shouldn't be 'fanatical' about their beliefs. Who's the one imposing themselves in this situation and telling someone what to do? It's not any 'evangelical' that I can see.
Some folks (and in my humble opinion, MOST folks) reserve their faith as a personal experience. Even those without faith have arrived at that place by personal experience. Few folks want someone else trying hard to sell them on another faith. Their faith is theirs personally and not something to be marketed like toothpaste.
If an Evangelical wants to preach to me and I decline their efforts, I'm not the one imposing anything on someone else, it's quiter the opposite. I don't want someone else's faith dictating public policy, I'm and American.