"If one subscribed to your argument, then if someone hired a hitman to whack a guy, he wouldn't be responsible for the hit, because he didn't physically do the thing."

hmm. You're changing the goalposts with the "responsible for" thing.

If you put a hit out on someone, there's a causality between your behavior and the ensuing violence, so it's correct to hold you responsible for what happened. But still, your behavior (of the soundwaves going thru the telephone or whatever) was not the act of violence.

Similarly, when you make an expression of voting, it's not an act of violence.

Allegedly, perhaps, the government actually responds to what a person votes for? (It would be on you to demonstrate that this is the case.) In this case, ya, then you'd hold people responsible for what they caused the government to do. But that doesn't mean their behavior was the act of violence.

(And I don't think you'd truly find a connection between making a vote and how the government acted. I know if I were to go to the fire station and select someone's name that I don't think my conscience would feel any burden by it. I'd just feel like I wasted my time.)