It's simply the politics of never giving in to your opponents.
Democrats went all knee-jerk in reacting to the George Floyd death by supporting BLM, "Defund the Police" and cashless bail as a way of showing solidarity with the African-American community. Now that they are seeing the results (rampant looting, public assaults, carjacking, subway attacks, police shootings, etc.) they are stuck, especially in an election year.
Democrats cannot admit to have made a mistake. They cannot be seen as "giving in" to President Trump or Republican policies for fear of Republicans running ads against Congressional, state, and city opponents that Republicans were right about crime and Democrats are soft on crime.
tl;dr: Democrats have made their bed and now they are going to sleep in it -- no matter what. To do anything else would be to show weakness.
-PJ
OK. That sounds very plausible. Thanks for pointing that out.