Yes, and, Yes!!! I just can't get started on the parents thing cause I dont think I'd ever be able to finish. I think there is a fine line between arrogance and an offering of your opinion to further collective knowledge with someone else. At the same time, a lot of people immediately get defensive and close-minded when their views are critiqued or opposed.
I think that it's perfectly okay to offer an opposing viewpoint, as long as that opposition does not lack respect for the other person's beliefs. However, when people blindly preach their own opinions without regard to the fact that they might not be the only one who's "right," or call someone else ignorant because of their thoughts- THATS when I have a problem.
Absolutely, and it took me a while to be able to catch myself when I start going down that road in a fervor about a subject. You could feel 100% right about something and be very, very wrong in reality. There's a nice cliché saying the first step to gaining knowledge is knowing that you know nothing at all. I am pretty sure Aristotle (cringe, i might be wrong) was credited with that.