Well it certainly depends on your definition of stupid and bad. I personally believe that people act very stupid, or come to stupid conclusions. I would consider that acting stupid or expressing stupid opinions is an example of bad behaviour. With that in mind, there was nothing concrete about that last statement. Bad and stupid are just adjectives. You need examples to make concrete statements, otherwise you're just saying stuff.
So....I think that some of the NT's I know, have stupid ideas (stupid in that I would not consider them to be beneficial to anyone, nor very logical). Their ideas lead them at act in ways that are bad (bad in that they disregard other people). Example: My cousin and my sister received money as a gift from my grandparents. (My cousin is 22 and my sister is 16). They decided that it would be fun to go out tanning (at a tanning salon) with this money. To me it is vain to consider tanning at a salon and stupid to waste money on it. Not everyone would agree with this, so my statement about people being stupid and acting badly is relative to what my values are.