I never understood the vindictiveness some people here have for IT. He tried his heart out and worked his butt off for the Celtics while he was here. Kyrie is an upgrade and Danny did the right thing for the team given the circumstances but IT wouldn't be the competitive player he is if he admitted that. It's natural for him to feel bitterness, anyone would in his position. He felt he gave the team everything and his reward was to be traded from a city and a team he loved. In his position would anyone feel differently from an emotional point of view?
The reality is that in professional sports nobody is owed anything other than the money that they are being paid. There's no loyalty in professional sports. Danny's job is to make sure the Celtics are the best they can be, in both the short and the long terms. IT probably forgot that, thought he had found a home here, thought he would be here as a long termer. He was reminded of the realities of professional sports when a better opportunity for the team came along and Danny took it and good on Danny for doing that. That's Danny's job.
But there's really no need to be vindictive towards the guy, he did the team, the organization and the fan base proud while he was here. It will probably take him a while to get over it and that's understandable. We can at least try to be gracious towards the guy.