Why are non spam comments on youtube flagged as spam?

Youtube has a lot of children and teenagers, and adults with similar mindsets, and many of them flag anything they don’t personally agree with.

Two main reasons: somebody disagreed and acted as a retarded 12 year-old (like @Kraigmo said) or the comment is visibly a troll comment.

I always wondered the answer to that myself. I see many comments where i think many of these a—h——s should be thrown right off from some of the garbage that comes out of their mouths and nothing is done than i see a comment flagged as spam and when i read it there’s nothing bad about it. I noticed it is very common for many people to not even talk about the video being shown but to just call other people names and harrass them for no reason. I couldn’t believe the trash that are in some of the comments and they allow it.