I'm not sold. Oh, I believe Ed's assessment. If it were me, I'd be intimidated seeing the dot on my body. I'm intimidated on an indoor range just seeing some other shooter's laser waving around down range.
But unless the perp looks down at their chest they won't see the dot. The visibility of laser beams is almost nil in the daytime and varies greatly at night depending on particulates in the air. Do you flash it in their face? How long do you wait for this reaction? How much closer will you let an assailant get before you realize the communication isn't working?
As a citizen, I think I should only draw as a last resort. By then it's too late for a "warning". LEOs operate under a slightly different ROE, I believe.