Simply because Bee wasn't prepared to fight from the start:
You must be registered for see images
They were discussing before Itachi suddenly attacked them with his fire techniques under Kabuto's control. Bee then explained Naruto what was happening. Unlike Naruto, he isn't a sensor, so obviously when he saw Itachi coming behind the Katon he just absorbed, he was surprised. Being surprised =/= being blitzed
This feat was impressive indeed. I can't deny that. But you must also take into consideration the fact that Bee hasn't shown to be that particularly skilled without other swords style than his own. He lost a taijutsu fight against Sasuke while holding Zabuza's sword for example:
You must be registered for see images
You must be registered for see images
Yet he dominated him with his own fighting style
You must be registered for see images
And with his own fighting style again, he was dominating Itachi in close combat
You must be registered for see images
This is a mistranslation i believe:
You must be registered for see images
Bee said "i know ok". He noticed Itachi from the start. He wasn't blitz at all. You can even easily notice how calm he was
True but this has nothing to do with speed. It was a genjutsu feat
Reason why i hate fanboys like you is that they can't argue normally without insulting others. Just like kids
Thanks mate but i think you confuse jutsu speed and body speed here