Are there some standard objections to the idea that option A is better than option B?

The reason to prefer option B over option A is the standard considerations of "suffering is bad". On most consequentialist considerations, a life of entirely suffering is not worth living. Would you want to exist if the only thing that would happen to you is torture and then death?

Your example with John Beatmykids is a good one.

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Another objection might be that there's always a choice C, but here I don't see another option as realistic.

Choice C might be to raise animals that are engineered to not feel pain.