No, the reason they're so trigger happy is because they're taught to be scared even while they're armed and given sweeping legal protection in all but the most bizarre extremes of malconduct. Being allowed and protected when they unnecessarily escalate situations for the sake of quick/easy resolution is why they do it. Its less a 'reason' and more an 'excuse', lack of self control, and being enabled when they fuck up. I'm no fan of the shit like the military but if they fuck up even a fraction of the degree of a cop, they get held accountable. And these are people who usually got suckered into the life by some recruiter, but most still keep their discipline when active.
Being armed, outnumbering, trained, and frequently the one initiating and escalating, a massive slice of that shit is rarely a rational or reasonable response. Especially not when the outnumbered, untrained and (actually) scared who are facing a group with a reputation for shooting people, will always get the entire book thrown at them for so much as punching an officer who is deliberately over-flexing their arm to get a response. Used to be a respectable profession, but the 'bad apples' were covered for and rose through the ranks, ending up covering for more of them, and fucking the whole barrel.
Cops don't need you to regurgitate in their defense, they already have the system, tax money and the bootlickers doing that for them.