I don't think he ignores him intentionally. First of all, he doesn't really know him, while he does know Naruto and Gai.
Second of all, I think Kakashi assumes Bee knows how to handle himself in a fight. After all the reason why Bee is there in the first place, is because he was training Naruto and decided to help him. They wouldn't have trusted Naruto's training to someone who they thought was weak.
So Kakashi probably thinks he doesn't need to give Bee instructions because Bee knows how to fight and to handle himself and Hachibi in the fight.
That's just my assumption though.