As someone who does devil's advocacy a LOT, part of the point when I do it is to make people understand that the issue is not as simple as they feel. It's not a never-ending game (for me), it ends when the other person acknowledges that their "solution" works in most cases, but falls apart on the boundary, or that it's a good idea but has a flaw, or whatever. In other words, with me, it's not trying to say "I'M RIGHT AND YOU'RE WRONG" but more of a "Have you thought about all the angles?" kind of thing. If people say "yeah, it won't work in all cases, but it's a pretty good solution and I haven't thought of a better one" then that's the end of it, for me.

Most people say "but it's a good idea!" as if that's all that mattered. I acknowledge it's a good idea, but I point out where it's not and folks take it personally, refusing to admit that their idea isn't a blanket solution.