Because that's ridiculous and exactly what foreign adversaries would love to see as a result of the currently tense political environment.

Plus, violent protesters almost never come out looking good. Any violence coming from the left would just entrench the powers of the right.

There are a few exceptions, like the revolutionary war. But, that's a time when American people were separated by great distance from its governing body. Revolution doesn't work when you're connected by land. Some foreign power would just take advantage of our weakness, and all Americans would lose.

We need to find a way to work together.