It's not just the potential blindness that is the problem. You also have to consider the distractional value of such a device. Typically, these lasers are shone at aircraft operating closer to the ground - the time when we are changing speed, configuration and being steered clear of other traffic and obstacles. These devices make it more likely to for crew to make an error. If just for that the little gits who shine these things at people need their nuts removing.
PM