Presumably the good Colonel had access to reliable, accurate figures.
Perhaps he was horrified enough by these figures to believe that they should be more widely known?
Not his call, I know. Certainly not his place to pass on the figures. Not his place to circumvent the normal chain of command.
But on a more visceral and less legalistic level, I find myself unable to fundamentally condemn what he did.
Did he put allied lives in danger? Did the truth damage our long term interests - or would trying to hide it do more damage? Better that civilian deaths are known about and that greater efforts are made to avoid them in future than to cover them up and continue in the same way, I'd have thought.