Stalberg isn't piss poor defensively, has a solid snap shot, and actually does have some hockey IQ. He doesn't have the best hands right now and he is mostly north/south (creativity) - those I agree with. I have no problem with a player getting the puck to the net, weak or solid, because getting the puck to the net creates opportunities. Driving the net like Stalberg does, which he is actually good at with his speed, creates a lot of opportunities because he either gets dragged down (penalty), gets lucky and buries won (goal), or creates havoc in front of the net (rebound/assist), or just creates an opportunity.
Honestly, he is a decent 3rd liner in the league and has started to accept his role on this team (hell, he got into a couple fights at the end of last year). I think the hate is because certain people expects him to be amazing because of his speed. His speed is one of his attributes and helps him cover up a lot of other flaws (several of the ones you point out aren't a big deal at all because of his speed), but his speed alone doesn't make him a top 6 forward (and that's why he isn't one).