Explaining jokes

It kills the joke. But sometimes it may be necessary. So what is the solution?

And is there any way to make jokes politically correct? Especially if they contain the following characters:

The stupid: often blonde or Irish, is lacking in intelligence and knowlege.

The thief: takes anything and doesn’t think twice.

The thrifty: sometimes Jewish, often Scottish.

The winner: At the end of the joke, he’s better off than any of the others.

P.S. My post may seem unclear, but that may be because I am asleep right now.