That's the point of most humor: you exploit a stereotype to get a laugh. As a rule of thumb, the difference between classy humor and not-classy humor is that

That's the point of most humor: you exploit a stereotype to get a laugh. As a rule of thumb, the difference between classy humor and not-classy humor is that with the former, you put the joke on yourself (not on others) and/or you point out that the stereotype has holes in it the size of an NSA machineroom.