I can't imagine what it would be like to be a LEO in this day and age. Especially in what appear to be routine traffic stops, vis-a-vis the video of the officers that were killed that
@mdwest posted. So I'm very reluctant to give an opinion with no experience whatsoever as to the right/wrong of the officers actions in the OK incident.
Having said that, I see a couple of things I'd comment about.
First, I have at least two incidents in my lifetime where I guess I got out of a ticket I deserved. The first time was when I was pulled over by an officer who was driving one of those D.A.R.E. cars you may have seen. D.A.R.E. standing for Drug Abuse Resistance Education. My wife and I were on our way to dinner and a Santana concert, first time we'd had a date night in quite awhile. My parents were with us on their annual winter escape from my brother's house in New York. I had actually passed the cop and was completely oblivious. Fact is I wasn't going that fast, but the people next to the cop kept looking at me and back at him. He told me this after I'd stopped. I kind of chuckled, not in a disrespectful way but just at my own dumb luck. So I said to the officer, "So you had pull me over mostly for P.R. reasons. He affirmed that. I then said, "Well officer, I can't and won't argue with you, truth is I've no idea how fast I was going. So if you have to give me a ticket, I understand you're just doing your job." As it turned out he was going home from having given a lecture at some school and forgot his ticket book at the school. He explained that and didn't really want to write me one anyway, and said to just slow down and enjoy the evening.
The second incident in the middle of nowhere in Arizona when I was hastily driving my father-in-law's truck back to Dallas. He and my MIL were visiting when my FIL died unexpectedly. I was doing probably 75 in a 60mph zone. I explained to the officer the situation but again in a respectful way. I knew I was speeding and he had me dead to rights, but given the situation and I think also how I handled it, he let me go with no ticket.
I think if this elderly man in OK had handled the situation a bit different, he most certainly would not have been taken to the ground, maybe he even gets out of the ticket.
Having said that, the optics of this looks horrible. I would not be surprised if in a civil court, the police department ends up making a big payout to the man. Right or wrong, that's just the nature of how things are at least in the USA.
Again I'm not going to say whether the officer was in compliance with protocols and the law, that's for someone else to decide and apparently has been.
But when a 70 year old man gets flung to the ground and requires being hospitalized for injuries caused by the incident and it's over an illegal U-turn, that is just not going to play well in civil court for either the officer or the department.