Itachi seems to be underestimating Killer Bee.

[ixc]

Itachi is fodder.

Naruto, Nagato and Bee would solo his ass

Naruto and Bee were saved by Itachi, Itachi had to guid them in their fight against Nagato because they were too stupid to do anything on their own.

Nagato got sealed by Itachi.

Itachi had to warn Bee not to look into his eyes, if Itachi wanted to he could have used Tsukuyomi which can only be broken by a Sharingan user.

Bee and Naruto are way too stupid to fight against the most intelligent character in the whole Animeworld, Itachi Uchiha.