I do find some lights are a bit over the top, especially on the well lit cycleways that I use. Runners and walkers too, not just bikes. I had some stupid arsehole staring right at me on the trail head a while back. His lights were all the lumems blasting me and I asked if he would mind not staring at me in a polite fashion. He was dismissive and after a few back and forwards about the matter it escalated to near physical violence. It took a lot of will power to de-escalate it (who wants to be in the paper as the bully that pummelled some poor accountant/Dr/lawyer, judging by his bike choice, despite any realities of the situation?) and then he came back and deliberately repeated the action afew times. Some people have been excessively empowered by our legal shaming of violent solutions to problems. I'm not a violent person, but sometimes...
I have seen a number of Off road strength lights used by commuters along a busy bike path I use a fair bit to get to riding areas.
Their lights are a bit bright, but they are gone in the other direction quickly and it's ceased to be a problem. it's not worth getting bent out of shape about. If there were three or four of them in a line, that would be different.
Your problem with old mate refusing to dim his lights or angle them down, after being asked nicely - that's different, and fucked. sounds like he was lucky to avoid getting punched. An expensive bike doesn't necessarily mean professional occupation, he may have been a coke/shard dealer, which might explain the aggressive attitude.
If I'm riding on the road bike, esp on the road, I will have as much light as possible - pure survival - , and I find that not only do the cars see me, but they tend to give me more space.
Runners and walkers on shared bike paths wearing their headphones and blasting tunes as they exercise can be a problem too. They can't hear a bike bell, but they will see a bright flashing light (behind them) illuminating the path ahead, letting them know that a bicycle is about to pass/overtake them.