I’m going to assume you are not a troll lol.

Its a frame from Indiana Jones. A movie about an American archeology professor exploring places for ancient artifacts.

In the first movie, he is searching for the Holy Grail but is also fighting a bunch of actual Nazis.

The joke here is that Indiana Jones is an actual professor in these movies. In real life, college professors tend to lean politically left.

Meanwhile, hes beating the shit out of a Nazi. Modern day Nazis adore Donald Trump and so obviously lean far right.

So Indiana Jones beating up a Nazi is like a leftie professor beating up and an Alt Right Trump supporter.

Its not funny since I have to explain it now. But on the 0.01% chance you are not a troll, at least now you know