Are you suggesting that laws don't matter? Clearly laws do make a difference in more ways than I could possible hope to enumerate here.
First, laws do change behavior for most people. Just look at the number of people that stop at red lights even when the consequences of running it (like when no one else is around) are zero, second, while we know that some people will violate laws anyway, doesn't that help determine who is irresponsible and careless, lastly, shouldn't the irresponsible and careless be punished? How can you punish someone for being careless and irresponsible if there isn't a law in place?
I have apparently missed you're example, but in most cases training does matter. Without knowing specifically what you are referring to I'll just say that cops are rarely taught to negotiate, and even fewer are taught when to negotiate. Most rely on offensive pre-emptive tactics. Increasing resources, additional weapons and gear leaves many cops feeling as if the people they are entrusted to protect are the enemy. Most police train in low intensity scenarios where adrenaline, distractions and emotion are NOT in play. Now I'm not saying all, but most. I was with a group that trained police in "continuance of force" techniques and the attitudes of most of the cops I trained was, when considering non-lethal tactics, poor at best. Most saw their sidearm as the ultimate negotiating tool. They are under the false presumption that angry, afraid, drugged, psychotic and otherwise uncooperative people are perfectly rational. The iron is that police suffer from the same kind of irrational behavior as is evidenced almost daily as new video's pop up.
Training does matter, but so does the kinds of training, the amount of training and the conditions under which you train.