Even as the rule is as you say it is now written and interpreted, which is very very stupid and open to abuse of interpretation, it still should not apply in this situation, because by him going there, he killed ALL OF THE COPS, and had he not, he wouldn't have. Banning him is like banning someone for thinking about doing a crime, even if you believe that was his intention. The end result, is all that matters, and the end result says that was the best tactical play to kill 100% of the cops instead of 90%.
But I repeat, he knew that cop was there. And saying he shouldn't have went in the pillbox is literally just saying he wasnt allowed to wipe the cops, just most of them.
And saying he had no choice but to spare the cop that was processing his friend to avoid killing his friend.