Life is not a high-school debate club. An _ad hominem_ accusation only really works if the attack is unrelated.

I don't know about ESR, but DHH has acted in ways that make it difficult to believe he is making a good-faith, unbiased argument on CoCs, which means I'm not obligated to reciprocate and treat his argument fairly. (DHH oversaw a list at 37Signals making racist fun of customer names, and overruled his employees who complained, eventually leading to a mass walkout.)

To put it in Bayesian terms, the prior that he's making a bad faith argument is higher than any random person, and should be treated as such.

I don't see how that is ad hominem - those are the expressed views of DHH and ESR, as they have repeatedly placed in writing, of their own free will.

They are also explicitly the type of views that CoCs are designed to protect contributors from, hence why DHH and ESR would be opposed to CoCs in general.