I have a hard time believing anyone in the music business wouldn't work with someone because of drugs. I know Michael Jackson was sheltered from reality but surely not THAT sheltered. The equivalent would be to say that a Hollywood actor refused to be on set with any actress who's had botox. It simply wouldn't happen.
Maybe the two didn't really click. Tried to record a few songs together and it wasn't there and the reason why they never finished the project was because there wasn't really the inclination on the part of one or both of them. Essentially it was a combination of a man used to getting his own way entirely and a guy who was a bit temperamental and used to having blazing rows over every tiny aspect of recording. It's no real surprise they didn't 'get on', is it?
Snackpot