That was a joke about USA assigning threatening labels to anything it threatens or exploits to make public afraid of it instead of being supportive of it. As most jokes, it based on the subversion of expectations, which in this case was the suggestion that hornets are good and misunderstood. Comparing them and what they're doing to bees to gay or black people was intended as a sprinkle of dark humor, implying their (hornets!) destructive nature finds parrarels with the multitude of oppressed kinds of people.
Way to tell me I'm unfunny and my sense of humor sucks, man (jk)
Nationalism as a function, to use your terms, doesn't have to specifically be a result of a desire for cultural identity. It might, but when speaking of it as a function it has a narrower meaning and doesn't have to carry additional baggage like that, though it may often imply it. When speaking of nationalism as ideology, it definitely fits my definition of evil, by putting artifical values above the wellbeing of people, which nationalism does by definition. Following that logic, nationalism as function isn't necessarily evil (though it may be if you flavor it with racism or such, like Confederation did), while nationalism as ideology necessarily is. I'm not sure what specifically you were disagreeing with, so I hope I made my point clearer.