You would think apostates from an ideology or religion would often be the most sophisticated critics of the old ideas, but in my experience, they are usually the dumbest. Why is that?
Suppose Bob spends 10 years as a proud, public advocate and scholar of political ideology or religion X. Then Bob converts to a new political ideology or religion.
What you'd expect: Bob no longer accepts X, but he understands it very well. When Bob discusses X, he is always very charitable toward it. He knows the best arguments for X and only describes the most sophisticated, steel manned version of X. He will have unusually good objections to X in part because he spent so long advocating it and yet changed his mind. He will have changed his mind because he encountered powerful objections to X, and he will be able to explain carefully to the smartest people who still advocate of X. People who still advocate X will find Bob's challenges, well, challenging.
What you actually tend to find: When asked about X, Bob will describe only the stupidest or most straw manned version of X. His objections to X will be objections that he would have laughed at and easily refuted back when he believed X. His arguments for views other than X tend to suck. People who advocate X will wonder why Bob ever believed X, given how stupid he makes X sound. Further, his description of what X doesn't match their own; he cannot pass an ideological Turing test for X despite having once advocated X.
UPDATE: One of my Facebook friends suggests that this is because people do not usually change their minds because of good arguments or new evidence. They change their minds for personal reasons, like they had a falling out or conflict with others who advocate X. This is of course not a reason to change one's mind about X in most cases. But people are flawed and ideology and religion are for most people more about identity and fitting in with groups than they are about the ideas themselves. So Bob, in his desire to rationalize his departure from X and his new identity of Y, will highlight the ugliest parts and worst advocates of X. It's no different, really, than when two lovers break up and then tell everyone how the other was really a monster all along.
UPDATE 2: As I think about this more, I should have added this: Most people who advocate most ideologies advocate the stupid version of it for stupid reasons. So of course we'd expect the typical apostate to be dumb for the same reasons the typical ideologue in general is dumb. But what I find weird, and what this piece is about, are the people who were fairly sophisticated when they advocated X, but then become dumb about X when they change their minds. You'd expect them to stay as sophisticated about X as they were before.