Automobile halogen lamps produce around 1,400 lumens. HID lamps produce around 3,000 lumens. So it's not the outright power of a bicycle headlight that's the problem, it is the beam pattern and setup. Most bicycle lights are simple spotlights with a simple round beam pattern. There are some makes that shape the beam and others that have a hard cutoff but they are in the small minority. My Cygolite Metro Pro has an oval pattern that I try to make sure that I point downward.
I'd argue that a 1,000 lumen bicycle light with a shaped beam that is aimed properly is no less blinding than an automobile.
Regarding blinking, blinking or modulating headlights on motorcycles came into fashion about 10-15 years ago. Anecdotally, they are much more visible. I lead motorcycle tours from time to time and have to keep track of a dozen or more motorcyles in my rear view mirror while I'm riding through traffic. The motorcycles with "modulating" lights are much easier to spot in my mirrors. If everyone had modulating headlights, then it might be chaos, but I'd hazard a guess that fewer than 5% of motorcycles have modulating headlights, so they benefit from being different.
NHTSA did a study about this. Here's part of their abstract:
"...having either LA (low mounted auxiliary) or MHB (Modulated High Beam) lamps on the motorcycle significantly reduced the probability of obtaining a short safety margin (< 3.44 seconds) as compared to the baseline lighting treatment....Eye tracking data indicated that the average duration of participants’ gazes at the motorcycle were significantly longer with the LHA lighting as compared to the baseline condition. These results should be interpreted cautiously in light of differences that were observed between participants who reported using a landmark‐based strategy to judge when it was no longer safe to turn in front of approaching vehicles and participants who used other strategies. Overall the results suggest that enhancing the frontal conspicuity of motorcycles with lighting treatments beyond an illuminated low beam headlamp may be an effective countermeasure for daytime crashes involving right‐of‐way violations."
SOURCE:
https://www.nhtsa.gov/sites/nhtsa.do...les/811507.pdf
Personally, I do run blinking headlights in the daytime on roads. I try to make sure that it's pointed downward though. Is it legal in my state? I'm not sure. But I ride through some busy places with lots of parallel parking and I need all the help I can get and am willing to risk a ticket in order to be safe.
Based on the NHTSA study, I may look for fork mounted auxiliary lights to add to my kit.
Lastly, if blinking has no effect on conspicuity, why do automobile turn signals blink?