First off, being bipolar it might be that his feelings for Slash may swing in correlation with mood. Secondly, his antipathy against Slash may be more directed against reunion and not so much against the person. Thirdly, even if he possibly dislikes Slash today it is still only human to remember old stories from their friendship fondly.
There you have it
! People seem to forget there's a difference between the work and the people performing it. Well said.
"If an album comes out, then buy it. If there's a concert you can go to, go to it. You're not owed another record, you're not owed any inside stories, you're not owed the band to be managed by people you approve. It's just electronically recorded vibrations you happen to like." (quoting Jplpool)