"Is he serious?"   Depends what you mean by serious. Yes, he's serious in what he's trying to get across, and no he very obviously doesn't mean the anti-everything ethnic crap that he presents us with.

The last couple of frames indicate very clearly where he actually stands - he's saying the real enemies of us all are the clean-cut naizis who'd destroy the world in the cause of cleansing it from ordinary screwed up mortals of every race and colour.

Whether his way of getting this message across is the best way is a matter of opinion, and I'm not sure what my opinion is, and in a world and a country where people aren't always that adept at reading between the lines, it's bound be be taken the wrong way. But taking it that literal way is the wrong way to take it.