Eh, I don't think he meant harm. Some people just do not understand 'how things work'
I did **** like that all the time when I was 16, and then I learned to be embarrassed really young. I do not think he meant it as any kind of affront to you (the bass player), I think he simply dug it and wished it was his band!
Hell, these days I always 'want in' on my buddys' projects! I've subbed for some, taken the place of some entirely, and cameo'd with non-bass groups, and if I didn't ask for at least a few of those in embarrassing ways then let science strike me down!!
Granted, theres a grey area that I mind carefully, and he did cross it, but I would just take it as a compliment, or at least as motivation to kill it every time!