If this is the guy who did that tv doc he's being misrepresented.
He's not saying all dyslexics are thick or that there is no such thing as difficulty with reading, but that there is no real difference between those who are defined as being bad at reading and those who are defined as dyslexic.
His argument (from the tv prog) is that we shouldn't try to define a group as 'dyslexic', we should give equal help to all children who struggle with reading.
His evidence as I remember it is based on two things. Firstly it's distribution - there is no 'lump on the tail' of the curve as you would expect from a specific disorder - it's a smooth distribution along the scale of how good/bad people are at reading. Secondly, children who are just defined as bad at reading benefit just as much from extra help as the so-called 'dyslexics'. Dyslexia therefore becomes an empty term which means exactly the same as having trouble with reading. That's all.
FWIW as an academic I have taught some very bright students who have dyslexia and also one of my most talented colleagues has it, so I would be very sceptical indeed of anything that suggested that people with dyslexia are thick.