I haven't always agreed with them, but they have always cooled things down nicely without resorting to violence or even arrests.
Training varies widely by locale, but I believe de-escalation is indeed a nearly universal part of their training. It must also be noted that de-escalation certainly is much easier for the police officers themselves: less hassle, less danger, less paperwork, less repercussions. These people generally just want to get through their shift and get home.
They are certainly capable of de-escalation and, in most instances, are trained and motivated to de-escalate.
So, it's very telling when (nearly always white) officers leap to unnecessarily violent tactics on (nearly always Black) victims.