It's not there as 'proof' - it's the data he put together. If you disagree with it, put together DIFFERENT data. (Bungie believes they made a mistake with the Halo 2 BR - it's why they added a shot spread to the Halo 3 BR. It seems silly to say "well, the Halo 2 BR has perfect accuracy, so clearly the Reach weapons should have that too" - why would Bungie go back to a model they considered broken?)
My biggest problem with the bloom argument is NOT whether you're more or less accurate with a given weapon than you were with that weapon's analogue in a different game... it's that folks are suggesting that the BLOOM is what's causing the inaccuracy, rather than it being what SHOWS the inaccuracy. Bungie could eliminate the bloom indicator, would that make you happy? You didn't seem to be unhappy with the Halo 3 BR - and it works exactly the same way, except without a visual indicator of the spread. If you space your Halo 3 BR shots, you will get a smaller spread - does that somehow mean that not spacing your shots makes you a 'trigger-spammer' or a noob?