Once you yell in an argument

you have admitted defeat.

No argument or debate needs to escalate to this point. If you can't prove your point without losing your temper than you have lost. If you can't reason under civilized conditions than clearly you have not and can not prove your point.

This is just the same as when parents hit their children in an argument, not to punish them that is a different topic. If a parent is trying to explain a point to their child but has to lose their temper and beat it into the kid then clearly no point has been made. The child will learn through fear and not through reasoning. Instead of the child thinking, "Oh, I can't do this because it is wrong because so and so" the child will think, "Oh I can't do this cause I'm scared of being beat." Is there a lesson learned?