If you have a belief about something, why do you feel the need to justify it?

May be the answer should be "why not". When someone asks you why you believe it, the choices are: a) to ignore the question and walk away, b) to tell the person that I don't need to explain it, or c) to explain it irrespective of whether or not the person responds positively or negatively. Effectively, there is only a 25% chance that this will be beneficial for me socially. But, it is compelling to explain it to someone whom you know well enough, that you've had at least 10 or more conversations with, because you want them to at least know about it even if they will never buy it.

Because it p!sses me off when people only believe in something so they can say they do.
If you're going to believe in something, you'd better have logic and reasoning behind your belief.

I used to "believe" in things and have "faith." Now I am present and experience things without judgment. It is not important to me to believe in things, just to be present and experience things.

Religious beliefs, because their religion tells them to. Scientific and medical ones because they're helpful, spread knowledge, and is the entire point of practical research.

I never feel the need to justify my own beliefs, but am willing to explain, if someone cares to know.