A Jewish man walks into a pub and sees a Chinese man sitting on a stool at the bar. He walks up behind him and clocks him on the head so hard that the man falls to the floor.

"What the hell did you do that for?!" says the Chinese man.

"Pearl Harbor," response the Jewish man.

"What?? That was the Japanese, you idiot! And that was more than 60 years ago, besides!" yells the man.

"Chinese, Japanese, whatever," retorts, the Jewish man as he heads for a stool at the other end of the long bar.

Before long, the Chinese man approaches the Jewish man from behind and bashes him in the head, knocking him to the floor.

"What the hell was that for?" he asks, though he knows why.

The Chinese man thinks for a bit and then says, "The Titanic."

"What the heck are you smoking? How could I be remotely connected to that disaster?"

As he walks away, the Chinese man says, "Greenberg, iceberg, whatever."
I can explain it to you but I can't understand it for you.