One helpful thing to keep in mind as a retort-stopper is that you won't "win," you won't change anyone's mind, you won't change any votes, you won't make the atmosphere in the room any better, YOU won't feel any better.
Carolyn HaxApparently you have ample proof from experience that you're not going to stop world evil by debating your in-laws into submission, so it's okay to choose not to try.
Carolyn Hax