You're being overemotional

[robvalue]

I agree that "being emotional" in no way equates with "being wrong".

I would only refer to your emotions if I think it may be a reason why you are wrong. For example, I think your argument is invalid and feel that maybe you can't see it because of your emotions. I would say it more tactfully than that and only where it seems appropriate :p I try to just stick to the subject as far as possible.

Face to face, if someone is getting highly emotional, I tend to suspend any sort of debate until they have calmed down. I'd try and comfort them, or appeal for calm, depending on the emotions displayed.