tl,dr: No arguments about the main point.

Let me count some scenarios:

* a miner losing its share in the competitive game could make a one last money grab before its hardware is obsolete

* BCash backing miners losing confidence in success of BCH could just damage the whole space, for revenge or and profit

* complete outsider like an angry government could try to disrupt the space to ban all crypto or at least heavily regulate it / buy some time

You don't have to risk anything. If the trend continues, at some point one would be able to rent the mining power required.

On top of it, if you are a small miner, and you can't afford capital investments required to keep up with latest mining hardware, while loosing market share, you can use your soon-osolete hardware to make a one last buck. A big buck this time.

Please re-read the post, because you don't understand.

The 51% attack is carried in secret. Noone has any way to know if it is happening until the longer chain is published. And after that, it's too late already. Someone could try to catch up with (not anymore secret) longest chain, but the damage has been done - the state of the network has already changed. Actually switching it back is only adding salt to the wound. Noone would trust that coin again anyway, and it is worthless to try to rescue it.

AntPool is busy mining Bitcoin, because it pays better:

https://blockchain.info/pools

so it can't constantly police BCash chain by over-provisioning it.