The rating system here
(reputations) is not designed to express agreement or disagreement with another post. It is a way for us to pat someone who gives good advice or makes a valid point a pat on the back. Conversely, if someone is rude offensive with a post, it's a way to keep him/her in check.
I have given quite a few positive ratings to posts that I didn't necessarily agree with, but felt the post itself was well written and expressed those views in a respectful manner. When I want to express my agreement or disagreement with a post, then I simply reply to it and offer my perspective.
As for anonymity, it's pretty tough to achieve, as this
is the internet, after all.
=)