I think it's certainly not worth writing people off over political differences, or even displayed ignorance. I think most people have a bias about something and will display their ignorance if you ever hit that topic, politics or otherwise. I think it's better to find common ground and let that be the general tone of your conversations, and only tread into disagreement if there is mutual respect and a willingness to grow through discussion.

Of course, if the other person is such that they simply cannot exist without shoving their different opinion in your face in an aggressive and uncomfortable way, it's probably not worth hanging around them. You just may have compatibility issues- nothing wrong with that.

But if I wrote off everyone who I thought made silly arguments about stuff, I wouldn't know many people. And I'd probably have to write myself off if I was honest about it.