do we have to AGREE with a post to nominate it?
No, it is not necessary that you agree. However, the nomination should express why the message deserves nomination. It should not express why you disagree with it, though it is okay to mention that you disagree.
I had similar reservations to those expressed by Adminnemooseus in
Message 5. The problem was not that iano's message was nominated, nor that Legend disagreed with the nominated messaage. The problem was with using "a classic example of a blind, unfaltering, dogmatic mindset" in that nomination message. If, instead, it had said "a clear expression of a creationist viewpoint" there would have been no criticism.