If not quite meaningless (though very nearly so), you both should remember that your two votes are almost certainly meaningless, and if anything, they cancelled each other out. From a practical standpoint, someone voting for the other candidate means next to nothing.
I can’t imagine getting worked up or upset at how someone else voted. Yes, political conversation can get ugly, but tell the visitor that you have no intention of debating politics if it means getting worked up or upset. And then stick to that.
All of this is magnified by 100 this time around. How anyone can get excited at the thought of either of these two cretins winning is beyond me. A pox on both of their houses… and both of their parties.