I think you have some valid points but I do not think there is a strong connection between voting and participation in violence. It might be a good topic to debate with a hardcore pacifist like a Quaker that also votes.

About the futility of voting against the mob/majority: Although a vote cast for the losing candidate has no direct effect, there is a feedback effect for the politicians and political operatives that represent the mob. If there is more competition, they tend to govern with a more compromising approach.