That's an interesting - and telling - quote.
It is interesting, because Penn seems to consider third party candidates - Badnarik is one - as "loony". That means he thinks his own political conviction is "loony".
It is telling, because Penn seems to brush aside all other political ideologies as possible except the Republicans and Democrats. He cannot fathom that people might find other ideologies worthwhile. It's either the two "evil" ones, or the "loony" ones.
I think I spot a pattern with Libertarians here: A profound dissatisfaction with life. It is everybody else's fault, everybody else is stupid and evil, only Libertarianism can save the world.
Let's assume that very few people vote. I'm not sure if there needs to be a certain amount of people voting before the election is declared valid, but if there is not, it would only mean that those who did vote - a very small minority - would grab all the power.
Penn seems to advocate "Divide and lose".