In reference to an argument or disagreement and assuming only one of the two people is in the wrong. There are usually two sides to every story.

The tango is a sensual, close-contact Latin dance which requires the couple to dance intricate steps almost joined together in unison. It can't be performed solo.

To me this just means it takes two people to do whatever is being referred to, saying "you cant do this alone"

It just means that certain activities require two human beings doing it, to be either "possible," or "enjoyable."

This would include:

Arguing
Boxing
Screwing

"Tango for One" just never caught on.