Imagine that a colleague is engaging in illegitimate political behavior toward you What steps might you take to reduce or eliminate this behavior?

Keep a written record, dated, time, and event. Talk with your human resources person or your union representative. Have the facts. Save anything done in writing.

You could start by saying you just aren't interested in the topic and would appreciate not having to hear about it. If that doesn't work, do a reminder. Be very nice. Don't criticize his views or make this personal. You are supposed to be able to work in the work environment and to concentrate on what you are required to do.

If this doesn't work, then go up the chain of command. All during this time, keep your records. They will be the evidence you need to make this stop. Step lightly and stress that this behavior is making a hostile work environment.