With flash LIDAR, the duty cycle is very low. A ranging cycle is about 1μs, while you might cycle at 60FPS. The chance of interference is only about 1/10000 for each ranging cycle. If you put a bit of random jitter in the flash timing, you can avoid accidental repeated interference. You'll get a bad frame once in a while, but if the frames on both sides of the bad one look similar, you're OK.

You can tell if someone is aiming a big light source at you; all the pixels show the same range, probably zero.

Those rotating machinery Velodyne things may not be as immune, but that technology isn't going to be high-volume.