The problem with this specific situation is that Kapanen had the highest cap hit of anyone in the bottom six, and they needed to clear that space in order to active Rutta, who is far more valuable.
Carter is the next highest cap hit and has a full no movement clause. Nothing can be done with him, even putting him on waivers, without his approval.
McGinn is the third highest at $2.75 million. The issue with him is you have two more years on his deal even after this year expires. So getting anything of value for him is going to be a challenge because of that length of his deal. You can bury him in the minors, but you only get $1.1 million of cap space for that, and it doesn't solve your longterm issues with the contract.
Hextall is responsible for all three of those contracts. That's why people are upset with Hextall more than Sullivan's usage of those three particular players.