Seeing the meth addicts and schizophrenics (and probably some who are both) who get so out of hand that police get called, dealing with them is a dangerous job. I'd rather train police better, than get body armor for a psychiatrist so they don't get bitten by someone having a "mental health crisis." Also highly trained mental health professionals are going to cost a lot more than police, and they probably won't want to work nights and weekends.

Also, when cops are called due to a "mental health crisis" that is sometimes because that person has caused enough alarm that the people around them are in legitimate fear for their safety. Unless the "mental health crisis squad" has lights and sirens and 911 can dispatch them quickly at all times, they won't be sufficient to deal with the problems. When they can't talk them out of their delusions and get physically threatened as well, they'll probably just call the police.

DTP is operating from an attitude which assumes that police can't be better trained and that this other group of highly educated professionals should be turned to instead -- explicitly to replace police jobs, which is to be expected since it's a philosophy primarily promoted by the elites (college educated). Al lot of law-abiding regular people of many races and backgrounds, actually don't have toxic relationships with the police and don't want less policing.