It seems to me that nothing should compel you to identify with the killer cop & explain away his use of force, perhaps unless you are a cop already, which you aren't. On the contrary, the point is to try to get cops & soldiers to stop thinking that their duty is to beat up protesters & shoot them dead, start thinking like you, & refuse to defend the machinery of oppression, for instance like conscientious objectors in Israel & elsewhere. Even before going so far as to join the other side (which would be revolutionary), cops & soldiers should be encouraged to *retreat* when confronted by the masses, whether they are engaged in civil disobedience or throwing rocks.
Though today's protests against supranational institutions of capitalism are far from reaching the level of anti-apartheid struggles in South Africa, we may still learn from what the ANC did & said then:
***** South Africa ANC Official Views Street Violence, Political Unrest
From London The Guardian
Report on interview with Joe Slovo, "Chief military planner of the African National Congress": "The Monolith Cracks" by Jonathan Steele
... In May, the ANC issued a call to black policemen to refuse to shoot other blacks, and "to organise secretly to turn their guns on their masters." People were also asked to steal weapons from within the system, to reduce the ANC's previous dependence on weapons brought in from outside. The ANC is now forming small, mobile units in the townships....
<http://www.sacp.org.za/people/slovo/street.html> *****
***** Take the Struggle to the White Areas
Make the whole of South Africa ungovernable! Paralyse apartheid!
... We must intensify our campaigns against conscription, repression, the tri-cameral system, racist education and the mass carnage by the army and police in the townships....
...Within the army and police we must refuse to shoot our fellow countrymen, and turn our weapons against the sadists who order us to kill and to maim....
<http://www.anc.org.za/ancdocs/history/ug/pam8500.html> *****
Since the state of affairs is today far from revolutionary, we can't urge cops & soldiers to "turn their guns on their masters." However, it makes a lot of sense to try to create a surge of the public opinion against cops & soldiers shooting to kill rock-throwing protesters, for the public opinion against repression makes it easier for them to refuse to shoot & to retreat instead in the future, especially in cases in which they are *not even explicitly ordered* to kill & maim. For instance, we should try to make it politically impossible for the government to arm cops on a riot-control mission with live bullets.
Yoshie
P.S. Protesters, too, must start thinking more about creating a political organization with a political program & strategy. Beyond making the streets temporarily ungovernable (which is just a protest tactic), do protesters have any strategy *at all*?