I confess to only ever watched TW for the fun factor (and a soft spot for Burn Gorman ;) and never much examined it from an ethical point of view, but...yes. Most if not all of Jack's decisions are worthy of discussion.

I think in part the show does put him in a position where he is the one that needs to take the 'nasty' decisions - especially as opposed to the Doctor 'no killing anyone ever* attitude, so yes, he is a bastard, only they try to make him a lovable one, o'so conflicted and broody ../irony

As Spike Captain John said (I think it was him?), "once a con man always a con man"..that says a lot.