Ryan McAvoy said:

I think the double line is a problem. "Qui-Gon would never join you" to "I will never join you" is not right.

"Qui-Gon would never join you and neither will I"

or

"Qui-Gon would never join you and I won't join you either"

Would be natural ways to express that sentiment, of course Obi-Wan doesn't say that ;-(

The disgusted way Obi-Wan says "Qui-Gon would never join you" implies the second statement anyway.

I don't think anybody would be thinking Obi-Wan would say...

"Qui-Gon would never join you but me I'm flexible"

I never thought about it as the first line implying the second, and I guess it does. I could cut the second line, though I really like how he emphasizes the "Dooku" in "I will never join you, Dooku". And this little emphasis seems more powerful preceded by the "Qui-gon would never join you" line.