A HUGE problem with our world is that people fail to see things from the perspectives of others. This cuts in all directions. I don't disagree with what you've said about Lebron at all. He could learn a crap-ton by doing ride-alongs like you suggest. Conversely, this cop might have different opinions on the issue if he cosplayed as a black dude for a week.
Here's the problem with what this cop did. Videos like this damage the reputation of LEO's with the people they most need to build better relationships with. If you're a white cop policing a black neighborhood, this kind of thing is just as damaging to what you're trying to do as anti-cop propaganda is because it gives that propaganda credibility. This cop is now a caricature of the clueless cop with no empathy or ability to relate with part of the population he's supposed to be policing. It's all a big joke to him, and it reinforces that narrative that LEO's don't want reinforced.
I get it. People cope with the stress of their jobs by joking around, and it's not always fair to judge that from the outside. Who am I to judge what kind of jokes two special ops guys tell each other while on mission in Afghanistan right? But you know what, if those two spec ops guys make a video of themselves - in uniform - making fun of the local population that goes public, how does that look? Does that help us achieve our mission? Does that help the local population trust US forces? Or do we go into damage control mode? Does it increase risk for our forces?
How is this different? I see people argue that it's political correctness run amok. But put in context of the US Military in Afghanistan, it's not about political correctness. It's about achieving the mission. This cop's mission is to protect and serve the public. Making this video directly contradicts that mission, furthers anti-cop narratives, and further inflames tensions making his job more dangerous.