What is the word for when members of the same group attack each other?

I've noticed this in a few South Park episodes, so that's what I'd like to give an example from. I'm sure other artists have depicted something similar.

Note that I'm not necessarily agreeing with the opinions depicted in the following, I am merely using it as an example of what I mean.

In an episode called Go God Go they have depicted a future with no religion. In this future, there were only atheists and they were fighting each other over how they should be called. The rest is irrelevant.

In another episode, It's Christmas in Canada, in one scene, they depicted French Canada folks singing something along the lines, "there's no Canada like French Canada, the other Canada is hardly Canada". Again, an example of one nation fighting "itself."

Is there any word, phrase or term for this?

Solution 1:

infighting is probably the simplest

Solution 2:

It could also be called internecine strife / conflict.

Solution 3:

A split or division within a group is sometimes called a schism.