Blaxill is not a scientist. Nor is he a doctor, though he plays one at SafeMinds. Blaxill is a former businessman turned spokesperson for the anti-vaccinationist movement (Vice President of SafeMinds). Fancies himself a self-made expert epidemiologist. In the grips of extreme confirmation bias (science doesn’t support his views, hence scientists are probably mislead by their own personal interests – having no clue as to how a controlled experiment is carried out).
Liar, crank and conspiracy theorist (Big Pharma is out to get us – Blaxill actually terms it the “autism holocaust”), as discussed here; also a professional shifter of goalposts (without necessarily being aware of it himself).
Among his most prominent techniques are faking statistics to show an explosion in autism the last thirty years, and looking at new studies to determine whether they are scientifically "solid" or not (meaning he determines whether they can be interpreted as agreeing with his lunacy or not).
Diagnosis: Delusional and belligerent crank; relatively influential and quite dangerous.
On an unrelated note, here is a hilarious game; test yourself!