Physical or Illusion?
Is it a clone or an illusion? Most of them say illusion, so it makes sense you can attack them if your champion can fall for it.
My point: Pink wards and red trinkets shouldn't just reveal stealthed enemies, they should erase any illusions of champions. It's easy enough to spot the face Wu, LB, or Shaco when they have a blue or red buff, but that doesn't stop them from putting the "illusion" in front of them to abuse the birds-eye type view of the game and make it impossible to click behind the clone.
Just as well, Auto Attacks should definitely be able to target illusions, but skillshots should pass through. You can fool a champion, you can't fool an arrow.
Lovin' the backlash from the clone-champ players who don't want counterplay or sense to their champions.