I don't think you were rude, I agree with you. I only let mortars autofire when I am too busy elsewhere. Otherwise I am using barrage for extra rate of fire to saturate at target or use attack ground, third most used is to target in individual unit if it's part of an on the move blob but you do have to be careful to make sure to issue the stop command once they're out of range since you don't want your mortar running after them.
You can Press stop right After the Order to attack. You dont need to time it. The Commune to attack stays but it Chancels the Order to follow then if they leave range