I don't think you have to be (certainly I am not,) not to put much credence in Reaction. From the premise that political history is conventionally taught in a biased and flawed manner, it does not follow that Reaction is unbiased or correct.

Of course not; even if you reject the current conventional narrative, it still takes a lot of evidence to pinpoint Reaction as a plausible alternative (nevermind a substantially correct one). But Mathias was basically saying that the models and case studies of monarchy he studied in his history classes provided him with such a high prior probability that monarchy "doesn't work" that he couldn't imagine why anybody could possibly be a monarchist in this day and age. I was arguing that the evidence he received therein might not have been quite as strong as he felt it to be.