IMO it wasn't accidental, Carroll definitely swung his arm in around in Chico's direction. Admittedly it wasn't a full-on swing and only brushed the Spaniard's head causing him to go down as if hit by a sniper BUT Carroll shouldn't have done it
As football heads towards becoming a non-contact sport, players who make minimal contact with opponents end up red-carded. Look at all the red cards given out when players simply gently press their head into their opponents head and the opponent goes down as if he's just received a 'Glasgow kiss' (most recently Bradley Johnson/Loic Remy - Johnson's red card was rescinded upon review)
But as I said, why is Carroll the only one punished?
Flores simulated being struck at force across the eyes, nit brushed against the forehead.
Until the FA and FIFA sort it out and make it a 3 match ban, it'll continue ad infinitum.