For whatever it's worth, I appreciated his use of English. In this case I don't think I would have had trouble parsing 'post hoc ergo propter hoc', but about half the time when someone uses the Latin phrase for a logical fallacy (or other concept) I have to look it up to make sure I haven't misremembered its meaning. Trivial inconvenience, sure, but multiply that by everyone else in the same boat and surely it outweighs the extra effort/space taken to type out a slightly longer, easily understandable English version.