Ha!

"as a matter of fact yes, I am an economist"

That would certainly be very effective.

Either play on the "battle of wits" mode, return the hostility, do your damnedest to humiliate the other in a way that >makes you look good rather than petty, or try to bring the hostile arguer... well, not to your side, but to a neutral basis of >discussion.

I will have to practice this more, I think the third alternative is just to leave the discussion because the other person is just locked.