I went through the first URL and here is what I gather:
1) Kane likes money and is okay flaunting it. He's young and rich and he flaunts it. While I don't love that, there's nothing that is actually wrong with it. He will grow up. He was trying to be "cool" tweeting at Floyd Mayweather. It definitely wasn't cool and not the culture of hockey players. But it's not illegal or anything I haven't seen before.
It seems people don't love his take on the business. He is business first. While owners will buy players out, cut them, trade them to get rid of their contracts, etc... he is business first, too. Why is that bad?
2) Every other accusation against him had ZERO backing. Not a single real source or issue. A lot of it was based on people not liking his attitude. But there was 0 actual evidence in any of those incidents on the time line.
I don't think he'd mesh well with the Pens locker because it's a hockey first locker room, but I do think he could adapt. It really depends on if he's matured over the last 5 years. But people calling him a cancer and a bad influence are wrong. I'll look into the 2nd link you put out there.