i think that was the only way to stop the Uchiha clan, because they were goin to start a civil war and try to take over Konoha, i think if he thought there was a way to avoid killing them all he would have went with that option!!!!
I agree with undeademperor. if hr didn't, the uchiha would have gained a lust for power to prove that their clan was the best. Especially because a sharingan user is very else, even a non-uchiha sharingan user, like Kakashi for example.