I wouldn't really put the media-driven Kessel hate on the same level as what went down with E. Kane in Atlanta/Winnipeg.
I can't really remember any stories about Kessel having as serious of run-ins with his teammates or coaching staff as the stuff we've heard about E. Kane. Sure, Kessel hated it in Toronto, but I think he had some good friends as well. I think the entire Kessel-Toronto thing was the Toronto sports media doing what they do, and going full 24-hour news network/gossip/tabloid **** on a guy that was brought in as a high profile offensive player--but wasn't a fit to be a franchise cornerstone type of guy. Kessel's phenomenal, but he's by no means a guy you hang your hat on as a franchise. That's not a knock against him, it's just the reality. The Toronto sports media ate that **** up and turned the entire town and fanbase against him because he wasn't the savior they unfairly chose him to be when the Leafs got him. The pressure mounted, verbal jabs were thrown, and the two sides grew to revile one another to the point that Toronto was forced to move him.
As for E. Kane, there are multiple reports of him ignoring (admittedly stupid) team rules for dress code, skipping meetings, being late to meetings/practice, and having run-ins with teammates as opposed to reporters. Byfuglien specifically threw Kane's tracksuit in the showers when Kane showed up to practice in it, violating the team dress code. Another report about Byfuglien nearly coming to blows with Kane, and then forcing Kane to dress in the hallway because he was no longer a part of the lockerroom. Now, I can't confirm firsthand these stories, but I've never really heard/read anything from anyone saying they're false, made up, or exaggerated. Then, there's an interview with Kane doing some kinda behind the scenes, "check out my house/game day routine" crap, where he essentially says out of all of the guys in the NHL, he'd want to fight a couple of his previous teammates in Winnipeg (I think it was Wheeler and Ladd?). Sorta lends a bit of credibility to the reports that his teammates hated him and he hated them back. This doesn't even touch on the reports of Kane being a ********, drunk and belligerent at bars/clubs, or the whole (since thrown out I believe) sexual assault accusations.
I don't know. I think the only similarity you can draw between the two is that they both had extremely tenuous situations in the past with previous teams. Kessel vs. the Toronto media, and probably Carlyle, and Kane vs. his teammates. I think Kane's situation is a good bit more dangerous to bring in to a team predicated on everyone being super tight-knit, and every single person in the lockerroom buying in to Sully's preaching 110%.
But, like I've said before, the Kane stuff was years ago. If JR and Sully think that this team, with the presence of Mike Sullivan, Sidney Crosby and Evgeni Malkin, can fix E. Kane's maturity issues, so be it. The guy undoubtedly has baggage, but if we were to acquire him, that would mean this coaching staff (and likely Sid/Geno) would have spoken at great length about it, and believe that they could sort him out. Kane's physical ability, skill, speed and toughness are wholly undeniable--he's a potential stud on the ice. If the powers that be in the Penguins front office and coaching staff think that outweighs his potential for off-ice issues and lockerroom garbage, I'll defer to their judgement.