Tanks, well, APCs carry more people and are a lot more secure than squad cars. People are shooting through doors, windows, walls, etc before officers even reach the building- how would you like to be protected.
Do you know why police started using AR-style rifles? They were outgunned in the North Hollywood bank robbery and the two robbers were covered from head to toe in body armor. They had been robbing up to two banks a day up to that point. Part of the video is on YouTube-
On February 28, 1997, Larry Eugene Phillips Jr. and Emil Mătăsăreanu walked into a bank in the North Hollywood neighborhood of Los Angeles and started the clock on 44 of the most violent minutes to ever occur in Southern California. What was meant to be a simple North Hollywood bank robbery...
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Why do people not blame the criminals? This is a cause & effect situation- if the police didn't need better protection, they wouldn't requisition it and the Federal government wouldn't necessarily want to give it out but IMO, it's better than leaving a billion dollars of military hardware in a hostile part of the world.
As far as chemical weapons, do you know anyone who carries Bear spray, Mace, pepper spray, or anything like that? Tear gas is an effective way to disperse a crowd or get someone outside of a building without shooting them but yeah, don't bother blaming the ones who are holed up after a crime spree.
If people were more peaceful, nobody would be talking about this stuff.