Passion. Aggression. Fear. Agony.
If our characters are feeling and expressing that, should we not be proud of it!?
I think the idea is that if readers can't tell when our characters are being passionate, aggressive, frightened, or agonized unless we sprinkle the page with exclamation points, then we should look to see what our dialogue is lacking -- because most of the time (if we are doing it right) the words we choose should get those ideas across without them.
If we're leaning too heavily on the exclamation points, it doesn't necessarily mean that the dialogue is bad, but it could mean that (on some level) we don't have enough confidence in our writing to believe it will be good without them.
If either of those is true, it needs to be fixed before sending our work out to agents and editors, doesn't it?