A question @ladyrebecca: if we believe that the giants at some point populated the earth, why did they become extinct?

Good question. I don't know the answer, but I will try to have a look at the different theories out there, those that seems valid, because it's a domain where it's very easy to fall into all kind of speculation.
As for the giants' character, their representation as gentle is a modern, more literary one... but if at some point 'normal' humans coexisted with giants it's easy to understand how they got a bad reputation, we're always afraid of people that are different.