I wouldn't do it to people who are trying to be helpful and let it go once they understand they aren't going to make any headway. The game is for the truly obnoxious ones, who are both dense and ignorant, and self-deludedly proud of it. For me, the game is worth the time (but not too much of it) because it gets deeper into the pyschology of that kind of mind, which is always interesting. I probably wouldn't even play it too many times, unless a different psychological type shows up that I could learn something from. It could get boring very quickly, but there are people who do like that type of thing. After all, some spend a lot of time refuting the bible even though it's been done so often it's almost formulaic.
And what if several people on a message board played the game simultaneously with the same person? It might turn out to be a way to get them to either shut up or remove themselves altogether. Of course, some troll-types are too dense even to get that they're the [censored]. Some of ours may be like that. (edit: I see we have censorship here. Ah well. Insert "goat" and think "b.tt")
I agree that there's something to be said for good intentions, but not for insistence on those intentions when the person has been informed that they're unwelcome (not to mention completely mistaken).
I don't know. I think playing with them is sort of insulting (not to them, but to yourself). Why would you bother? And, in the end of it, they are (well some of them) honestly trying to help, albiet in a way I find rather silly. I know that some people can't be bothered with intentions, and I understand that stance, but I tend to consider intentions because while the outcome is the same I think there is something (I'm not sure what) to be said for someone trying to do what they think is right.