I first thought: "Why would you attack people doing yoga?"
Then it made sense:
the protesters brandished placards proclaiming that yoga was against the tenets of Islam.
I don't know what was in the minds of these Islamists, but I would guess that they associate yoga with Hinduism. And we all know about the violently antagonistic history between Moslems and Hindus in India, which led the the bloody partition of the Indian subcontinent. It's just one more example of religious sectarianism, and the violence that so often accompanies it.
doesn't make sense but does explain why the knuckle draggers felt the need to attack them