Rumors are sparks: gather enough of them and something's going to catch fire.
Incited Rabble's controller still chooses which player or planeswalker it attacks.
If, during its controller's declare attackers step, Incited Rabble is tapped or is affected by a spell or ability that says it can’t attack, then it doesn’t attack. If there’s a cost associated with having Incited Rabble attack, its controller isn’t forced to pay that cost, so it doesn’t have to attack in that case either. Note that transforming Town Gossipmonger won’t untap it.