It is problematic for sure... But Dooku could be simply trying to trick him into joining the Sith... Maybe he feels if he could just get him to join him "to destroy the Sith" then he can begin the brainwashing process... Because the thing about the Sith, every one of them wants their own apprentice. To what? Overthrow their master. Vader did it, not too terribly far fetched to think Dooku would want the same way. He's just sneaky about it.
May still be completely retarded, but it's slightly less than the current state of the film.