I think a therapist should not be debating politics with clients. That adds stress, which clients go to therapists for help to relieve. They also aren't there to try to convert anyone to their way of thinking on controversial subjects (politics, religious beliefs, etc.)

I think a professional acting therapist should be honest with a client and simply say that political discussions are best avoided, if the views conflict. If the client is OK with that, then perhaps the relationship can work. However, I believe that political issues have affected many to an extreme mood-wise and emotionally, and those facts alone are things to process. In the latter case, if it is, then perhaps a different therapist is recommended.

My most recent therapists (I'm between) had very similar views as me. My psychiatrist is a bit more conservative, but more middle of the road (Lincoln project type/or Michael Bloomberg type supporter). [Bloomberg has some Republican ideas and some Democratic.] That works fine and he has never ever debated me on anything political. He's always supportive and understanding. We respect each other for having our own viewpoints.