Well, this is a bit like parents who take their kids to get vaccinated and a few hours later that kid exhibits the first signs of autism. It's an immensely compelling coincidence. You'd have to (a) know that autism symptoms often have a rapid onset and (b) realize that when they do they can follow any commonplace childhood event. Even if you did it'd still be hard to shake the suspicion if it happened to your kid.
Somebody points a IR remote at your friend; he gets up and has a brief moment of orthostatic hypotension -- also known as a "dizzy spell" brought on by a sudden drop in blood pressure -- just at the moment the guy pushes the button. Orthostatic hypotension can happen to anyone, but if your friend isn't otherwise prone to it that can be a very compelling coincidence; and many of the symptoms of hypotension can be reproduced by psychological stress.
If something like that happens to you people will say, "oh, it's all in your head," but the thing is that all suffering is inside peoples' heads. One of the worst kinds of pain you can have is passing a kidney stone, but if you happen to be in a coma at the time you won't feel a thing. Distress produced within the brain is indistinguishable to the subject from distress produced outside the brain. Having an external explanation for that distress can make someone feel like they have some control over what is a disturbing experience, and shooting holes in that explanation isn't going to help unless you can offer them a better handle on it.
Sometimes I think we'd be better off if we just brought back shamans and witch doctors.