My Way or the Highway?

Why do you think human beings have a need to convince others that their way is the right way: Whether it be their views on religion, homosexuality, or birth control, etc?

Please note: This thread is NOT about what your views are on these topics (or any other), but rather, why people have so much invested in convincing others that their way is the only right way, regardless of the subject.

For example: In general, my feeling is that people who are vehement about pushing their opinion on a topic are trying to convince themselves more than the other person. Maybe their own faith, for example, is not strong and is easily shaken by someone believes differently.

I find this very true about liberal dems in particular. If you don't believe in their way they scream louder until you do. If you continue to resist, they get even worse.

They can't just not like someone or something and move along quietly. They have to protest, harrass, boycott, and even insult and outright lie to convince everyone that their way is the right way.

Just look at Pelosi. She pushed and pushed the healthcare bill until she got her way. Then when asked was in it she said, "We'll just have to pass it to find out how it will work."