Moron is probably an incorrect term, as his intellect is developed well beyond a 10 - 12 year old, and I should perhaps have used the word 'nitwit'.

Exactly .

Check out Rembrandt or Gaugin, Hepworth, Rie - he doesn't reach their ankles...

That's no different to saying check out Bach ,Bartok ,Beethoven ,Mozart .
When Hendrix ,Mcartney ,Tamla etc don't reach their ankles of course they don't who said he they/he did or that he was .