It's been ages since I've looked at the stuff, and I didn't fully understand it then, but my understanding is that beyond a certain point, air becomes increasingly opaque as more and more energy is pumped through it. A low power beam may be able to pass a certain distance through the air while being attenuated 10%, while a much higher power beam travelling the same distance might be attenuated 90% or even 99%. Because the power level required to blind someone is much smaller than the power level required to destroy metal, I don't think atmospheric attenuation would be anywhere near as major a factor as it would be with SDI.
Until the air ionizes it doesn't make any practical difference.
To ionize the air with laser light it take very large energy densities.