You can't be that stupid.
If a freeman or policeman dies in the line of duty at an arson fire, yes, the perp gets charged with murder.
Till you can grasp that fact, we'll just put the other two voices in your head on hold. Have them go offline and talk to each other.
We weren't talking about a fire, we were talking about policemen stopping traffic.
My comparison of children being responsible for a crossing guard getting hit is an equal comparison to you blaming the sign hangers for a policeman getting hit by traffic. Much more so than your strawman fireman/arsonist comparison.
If a policeman is hit stopping traffic for a car wreck do you blame the accident victim? If a policeman is struck by a passing car during a traffic stop do you blame the motorist he pulled over? In all those cases the fault for the injured cop goes to the operator of the vehicle that struck him. Just as it would for policemen risking their very lives to stop traffic for this advertising campaign.