At a minimum, watch 100 videos. I did last night, only took about an hour, it's easy to find some to nitpick, some which are ambiguous ... and plenty that are totally horrifying.
If you can watch 100 videos in a row from Greg Doucette's list and say, "the militarization and use of force tactics of US law enforcement are not a problem" then I'd like to hear why you think so given this evidence.
Otherwise you're not speaking from an honest grappling with what these videos contain.
Does this mean that people just do not care, or there is only some minority who thinks that the police is too violent and the rest is ok with that?
On top of that they're a fairly politically active group, so they have an outsized influence on policies, including those that affect them.
But the biggest issue, as you note, is the sheer disparity in who interacts with the police at all.
From a 2015 Bureau of Justic Statistics report
https://www.bjs.gov/content/pub/pdf/cpp15.pdf
Only about 10% of Americans had police-initiated, non-traffic stop contacts.
So 9 out of 10 Americans never see the police, much less have insight as to whether they're too violent.
Blacks 50% more likely than Whites to be subjected to a street stop by police.
Blacks 120% (!) more likely than Whites to be subjected to police force.
And, every single respondent who indicated they were Tasered by police felt it was "excessive" force.
So, yes, fundamentally this is a "rights of the minority" problem - and the minority in this case are younger, poorer, less politically connected, and therefore are underrepresented in discussions about police brutality, effective law enforcement, police training, and other policies which impact them.