Is a 'Can't be countered' ability the same as 'protection From' or 'Can't be targeted?'
"Can't be countered" spells are still legal targets for counter-spells.  They just won't actually get countered

and this was already answered earlier today with the gatherer Rulings from Render Silent


  4/15/2013     A spell that “can’t be countered” is a legal target
  for Render Silent. The spell won’t be countered when Render Silent
  resolves, but that spell’s controller won’t be able to cast spells for
  the rest of the turn.


and here's another ruling which will help illustrate the difference between illegal targets of a spell and can't be countered


  4/15/2013     If the spell is an illegal target when Render Silent tries
  to resolve (because it’s been countered by another spell, for
  example), Render Silent will be countered and none of its effects will
  happen.