What a crock. Rulk is a villian! Would Steve allow the Green Goblin or Abomination on the team because they want redemption? Hell, no. If anything, just put him on the Thunderbolts. Steve would make a smart decision in regards to letting someone like Rulk on the team. This may be a fictional world, but I doubt the writer would make that a scapegoat to allow dangerous decisions like that. Unless of course they want the shock value.
Technically, Hawkeye, Scarlet Witch and Quicksilver were also bad guys.
Same thing with Ares as well.
Yeah, Thunderbolts would be a good spot for him, but maybe Steve is looking at how they've consistently crapped on the Hulk and sees it as an opportunity to make things right. Surrounding Rulk with bad guys that he could manipulate would be a bad thing, putting him where Thor and Iron Man can keep watch on him, is better.
Of course, in all likelihood, there'll be some hidden backstory where Steve, Bucky and Ross served together or at least have some people in common.
RULK IS A VILLAIN. Rulk can have his redemption I said, but it doesn't have to start with a team of superheroes. Any character can have his redemption, but considering all the horrible things Rulk's done, consciously, it's gonna take a lot more than putting him on the Avengers. I'm only saying this in the context of the Avengers line. They can do as they please with him on his line.
Technically, he'd be an anti-hero. If you're using the Abomination's death as reasoning, then a lot more heroes would be classified as villains. Yes, he drew up the plans for the Intelligencia, but he also stopped short of committing to it and made efforts to stop them. Presumably, based on his actions in the comic, Steve realizes it's not a black and white issue and would rather steer him towards good than risk losing him to the bad guys again.
Either way, I personally have no issue with it. I can see where some could, but really, if Wolverine is in and some of the other past Avengers, Rulk can join too.