"In that case, the justification would be pretty clear in most every jurisdiction to respond with force paralleling that used by the perp."<--although that might be different in other states or areas....
State of Florida Use of Force Matrix indicates that an officer can use 1 level above the amount of force used by an attacker.
The officer the original poster was speaking with might have been in a LEO that does not see as much officer assaults that another officer in another area (such as NY) might see. Therefore he might be less inclined to engage as quickly.
He might also have an administration that is quick to initiate an IA even if in another agency the use of force might have been considered justified.
There are so many ramifications in LE it is difficult to make a hard and fast generalization that sticks for every LEO.
As far as, "tried by 12 then carried by 6". Most long time officers are aware of this saying, however, I'd rather make the correct decision and not be tried at all.
Below is Florida's Use of Force matrix....
i wanna make the right decision too. .but if i'm about to be killed, and i have to make a split second decison, that is what i was talking about.. sometimes you make that decision and you are 'tried ' anyway...
And therein lies the question...
"Do you love the job so much that you are willing to risk life and limb and or your family and financial welfare if someone sues you for something and you lose?"
Do the right thing...at the right time...for the right reasons...in the right way... and hope for the best. Whenever it gets to be too much, cut your losses and find another line of work.