I will answer the question this way. Suppose like stop and frisk law enforcement started stopping 50 year old white males on the streets outside banks and brokerage houses, searched their papers, computers and storage. Walked them back up to their office and start a random search of their files looking for violations of law.
That program would last 24 hours before the phone calls are made to the right person.
I picked 50 year old white male because it fits the profile of people who commit financial fraud that cost this country far more money then brown people ever could.
That's how I feel about the constant calls for more 'stop and search' here, to deal with the increase in knife crime (perceived as 'black-on-black', though that's only really the case in London, elsewhere its white kids doing the stabbing - as I see it there's a kind of 'ecological niche' that just happens, for complex historical reasons, to be filled disproportiontely by black youth in London, but in other parts of the country it's other groups who fill that role).
You would catch some knife-carriers and prevent some crimes, but you'd also prevent a lot of crime if you allowed random searches of people's houses, or searching motorists cars, but the same people who call for more stop-and-search of youths in the street would have conniptions at that. They're all 'the ends justify the means, stopping crime is all that matters' as long as it's not _them_ who are being targeted.
Even if you ignore the general morality of it, you'd have to account for the bad effects on police-community relations - it would likely end up increasing crime in the long run, by destroying all respect for the police or willingness to co-operate with them.
I've been stopped-and-searched a few times without any good reason and it made me pretty annoyed, and I'm not even black, so I don't get it constantly. When given that power the police go on fishing-expeditions, and they do so based on dubious judgements about people's appearance.