Generally, roosters (especially the dominant flock roosters) expect any chicks to be their own offspring. So they don't hurt them.That would be silly, and counterproductive to passing on their own genetics.
Hens, on the other hand, have no stakes in the survival of their rivals' children--those chicks might take up resources they'll need. So they're far more likely to injure the chicks. Angry momma hens are generally very capable of protecting the chicks, though. Especially when the chicks are old enough to follow mum around easily, and she's protective enough to flatten those that peck them. If the chicks are older when introduced, then momma hen won't be as protective, and integration will be harder.
That's my experience, anyway.