What if someone posts repeated answers to repeated questions?
What if someone posts something he does not know the truth, and only based on Opinion?
Are they Spammers

?
Depends on the context really, and how much effort is put into the post. There's too many variables to paint everyone with the same brush, and it would need to be taken as a case by case basis. Duplicate questions aren't too bad, and some times invites healthy discussion.