There is a distinction to be made...I don't think smart people are fooled more often, however...when a smart person IS fooled the consequences are much, much worse.
I recall a debate I had with a childhood friend of mine and undoubtedly also a very intelligent man, and he firmly believed that the Holocaust never happened...he is also I suspect a convinced nazist...but he would never admit this openly (because he is smart), and maybe he doesn't really think of himself as "one of the nazis" anyway - but more an intellectual descendant who sees things in a perspective they never realized.
Now...I should explain at this point that he does have anxiety and light touches of paranoia, and an unhealthy use of alcohol and various other drugs...so I don't think he came about this belief because he is smart...rather because he is isolated and needs the world to be simple.
However...the problem is that is, at heart, he is an extremely smart person
. Not only that - he is also well read, he does a lot of research, he is articulate, he is very meticulous...at high school he was always a top grade student due to his diligence and ability to digest enormous amounts of material in a short time. He didn't take any higher education due to his problems, but really he has all the qualities of a skilled academic.
So then comes the problem...he can with extremely skill defend the position that the Holocaust never happened. He knows historians better than most people who debates him, he knows logic better than them, he can name dates, people and whatnot. He never indulges in "cheap" propaganda of the type "jews made it up"...because he knows this would destroy his own argument. In short; he displays all the qualities of a good debater and superficially he seemingly possesses all the traits of a seemingly "neutral" historian.
Now...his case is ofcourse all shambles...because most of us realize that there simply isn't enough competency in the world to conspire up something of the magnitude of the holocaust....but you will never reach him because he is clever enough to destroy all your arguments...and stubborn enough to ignore their combined impact. So...for us the only option is to ignore him...however...in his "clique" of people (internet-wise) he becomes almost prophetic.