Is moral outrage manufactured? Or is it genuine?
It can be either depending.
Should it be considered a valid tactic in a political debate? Wouldn't moral outrage be an appeal to emotion, which is considered a logical fallacy?
Emotion is not logical.
I see moral outrage as a tactic calculated to elevate oneself to a position of moral superiority, which would give one license to judge and condemn others. Some might even see it as a political obligation to be morally outraged over something someone did/said which was considered "deplorable." Those who don't express the same level of moral outrage might even become suspect themselves.
There's the Luke Skywalker Return of the Jedi temptation is allowing one's sense of outrage/rage/anger to take control. People can easily become what they abhor.
There's also the flip side where being really upset about immorality is motivation to act in a positive sense whether that be at the ballot box, via personal work or whatever depending on the situation.