That problem will be fixed once we get robot soldiers.

I'd rather say that high income inequality leads to people realising class antagonism between the proletariat and the bourgeoisie, and the synthesis of this conflict is Socialism.

Violent revolution is manifested throughout human history, before there was even a concept of Socialism. They were called "slave rebellions."

https://en.wikipedia.org/wiki/Slave_rebellion

This is the point - it is class conflict, Marx took this into account in his materialist conception of history. The antagonism of proletarians and bourgeoisie is the modern manifestation of the class war; slave rebellions the ancient manifestation.