You don't. You care about what you care about.

What you can do is a combination of stone face and meditation.

Stone face is never giving a reaction of any kind. They shoot off their mouth, you just look away, walk away, or stare blankly at them. Should they question it, you just state you're going back to work (if leaving their presence), or "nothing" with nothing else added.

The meditation part is so that you don't crack. You learn to control your breathing, which gives you the later ability to both exist in the now without dwelling on the events of the now, with the side benefit of being able to tune useless signals out.

Both take practice. And they kinda depend on each other. You do stone face without meditation, you end up just eating yourself up inside from the stress. You do meditation without stone face, you end up looking calm and happy, which encourages the behavior.

Now, it's important to remember to do it when a person is voicing their silliness that you agree with, too. See, if you only go blank with one area of politics, or only that person's religious vomit, you end up causing problems for yourself. So hold everyone to the same standard that politics and religion are just utterly useless to bring up around you.

Are there cases where someone is going to push? Sure. You fall back to stating that you're hearing them out, but you have work to do. This does come with the consequence that you're going to have to also stay distant with other conversation and stay on task at work, at least verbally. That can be a loss if the workplace is otherwise relaxed and less "work now scumdog slave!", but it usually ends up being worth that.