The OP still hasn't expounded on what defines "passive" so I'm gonna go with good ol' Dictionary.com lol.
There are 3 main definitions given:
1. not reacting visibly to something that might be expected to produce manifestations of an emotion or feeling - meh...this could mean that he's not easily swayed by corny cheeseball things, or it could mean that he's got a heart like a dried up prune... the former is good, the latter is bad.
2. not participating readily or actively; inactive: a passive member of a committee - generally a bad thing, this sounds like a couch potato, apathetic, let-life-happen-instead-of-making-life-happen kinda guy.
3. not involving visible reaction or active participation: to play a passive role - would depend on the situation, but if his general life attitude was just "sit back and stare at the wall" then no, not an attractive thing.