Mindless fights for power need not be given a religious colouring. As you mention sects of Hinduism were also fighting against each other, clearly showing that this is not religion vs religion but that of power. In any case if these were genocides as your tones suggest, then I have news for you, Buddhism lasted out such genocides pretty well. Buddhism's strict ways of Hinayana Buddhism of destruction of self were too austere to be followed so Mahayana Buddhism came up which was more pluggable with local cultures to whereevr it spread. Thus we do not see a very distinctive Buddhist orthodox culture in most places but Buddhism lives nevertheless.
