Optimal persuasion was not my priority, emphasizing the nature of disagreement was. If deceptive use 'rational' was not a violation of both terminal and instrumental values then accusations of 'counterproductive negativity' or generally poor thinking, etc could be taken to have some approximation credibility - "it doesn't matter so you should shut up" vs "Direct attack on core values! Destroy!". I did originally explicitly explain things in these terms in the comment, including reference to ethical theory but that was turning into a seriously long winded tangent.

As for optimal persuasion, it would not involve a complete reply, a targeted paragraph responding to a cherry picked quote would be more effective. In fact, better still would be to make no reply at all, but create a new (much needed) post on the subject of ethics and rationality in order to direct all attention away from this one. Arguing with something gives it the credibility of 'something worth arguing with'.