Whether or not positive and negative sterotypes are used are kind of besides the point, its the fact that a stereotype was used at all. Let me give an example, if you say im a jew so I have money, os that negative or positive? Even if you think its positive, the fact that the stereotype is validated implies that other stereotypes are true.

Now this particular joke is pretty tame, certainly. If he wanted to he could have add the qualifier " more talking, bringing more perspectives to the table" or something. But the way he said it could have been interpreted as a stereotype, and therefore is problematic