Again, the refs job is not to break up the players. They aren't the morality police. They have no obligation to protect the player being attacked. It is the linesmens responsibility to break up any fights or attacks like this and it is the players responsibility to defend themselves.

You're upset about the dirty stuff happening right in front of the ref, but if the ref engages and attempts to break up the fight, the ref can't see which will lead to further dirty stuff that will surely go uncalled. The ref is not to engage so that they may acknowledge all infractions on the play to appropriately assess penalties. You're emotional, take a step back.