I think what google is trying to prevent is not dissenting opinion but rather things like the fact that 80% of newt gingriches twitter followers being fake. They want to create a community based on honesty and real world identities. if you need to post something anonymously on the internet, there are plenty of ways to do that. For instance googles blogger TOS doesn't disallow pseudonyms. So if you need to publish anonymously then maybe G+ just isn't the place to do it.

Real names is obviously a tricky policy to enforce but there is value in it. I think that eventually the policies and enforcement will converge on a better solution. This is probably one of the reasons G+ is still in field trial.