I think it helps if a T and client agree on some fundamental things... such as how abusers are looked at through the eyes of healing... And it is also important for there to be a human bond of some form - the therapy relationship IS a relationship.
But just like any other human to human relationship, there should be room for differences. Just because the T and Client are not of the same political party does not mean they can not work together. It may take more effort on certain things if the differences come up in the conversation on therapy... but just like any good relationship, those things can contribute to empathy between the two parties. Two people can remain two separate people but build mutual respect.