I have one of those double lamp cree chinese lights you can buy on amazon. Its very bright when its on full. I was testing it out in a park and I could hear voices in the shadows saying "what in the **** is that" as I rode along the path. Even my department store usb chargeable bike light is bright enough that I've had people flash their high beams at me when I have had it angled up. I'm fairly certain that at the right angle these modern led lights can impair the vision of oncoming drivers.
I generally conduct myself in as considerate a manner as possible when I'm one a bike because there is a great deal of animosity toward cyclists in Ontario, where I live. Since we are all rather vulnerable out there is probably wise for all of us. Luckily its not so bad in my smallish city but Toronto, my former home, is bat **** crazy with the tension between bikes and cars. I once had a guy in a car tell me I had brought a knife to a gun fight. He had a three year old in the car with him, observing the whole discussion.