Also, the more the country slips toward C+ could increase the tolerance for political violence, simply because organized violence from the government is so commonplace anyways. You have death squads executing people for petty crimes, the local fire department starts fires, rather then putting them out and you have the right-wing paramilitary CCS that spills blood in the name of Jesus and Capitalism. Machineguns are openly purchased everywhere.
That sort of society would be quite uneffected and would not be moved by violence.
Also, the disparity between the status of the current policy in effect and the public opinion in favor of it would effect the tolerance for violence. If Liberal or Conservative change happens too quickly and too drastically, people will be out in the street screaming for blood to spill and City Halls to be leveled.
Subtle, slow changes do not upset people as much as sudden drastic changes do. The PATRIOT act passed without a hiccup, the 94' Assault weapons ban passed with only minor bitching from the NRA.
But if you revoked the 1st or 2nd Admendment or you outlawed abortion or gave animals the same rights as people, you would have riots and normal people emotionally provoked to murder their neighbors, like what happened in the Spanish Civil War in 36'.
I think it would be super-neato if it was mostly rapid policy changes that inspire a tolerance for violence. If you start the game, stay low, and the Conservative nation swiftly steers right, the tolerance for violence would be high, same if you kicked the game off with the LCS steering the nation hard left overnight, the tolerance for political violence would skyrocket and the CCS would emerge faster.
Creating situations like wide-spread riots and martial law and the "Moderate Crime Squad" or coup d'ete type events in response to the player's actions or unaction would be awesome.
It'd make gameplay interesting, to keep the game from being easily lost through inaction or easily won through intense pursuit of the LCS's agenda where the public is not behind the Liberal idealogy.
The Martyr effect would just be the trigger. The people hate the policies in effect but don't take action, then your pacifist liberals spray a mural in the park, are executed on the spot by the cops... well, that'd start riots, like it did in Greece recently, or the LA riots back in the day. It wasn't that single beaten man or dead kid that caused the riot, it was just the breaking point for the people's tolerance for a system they hated anyways.