I highly doubt this is true but...here it goes.

I heard from one of my friends that the only reason why Syd did drugs because I guess someone he was friends with was friends with David Gilmour and Gilmour convinced his friend to get Syd into drugs cause I guess he knew that if Syd's habit got bad enough he'd be out of the band and Gilmour could be the new member. Apparently that's why Syd hates David so much but Syd never confronted him cause he knew the other members of the band wouldn't believe him. But like I said this probably isn't true.