The controller of a creature dealt damage by Aggravate still decides which player or planeswalker the creature attacks.

Aggravate targets only the player. Creatures with hexproof that player controls will be dealt damage by Aggravate if it resolves.

If, during a player’s declare attackers step, a creature is tapped, is affected by a spell or ability that says it can’t attack, or hasn’t been under that player’s control continuously since the turn began (and doesn’t have haste), then it doesn’t attack. If there’s a cost associated with having a creature attack, the player isn’t forced to pay that cost, so it doesn’t have to attack in that case either.