Not only was he doing that, he called everyone who isn't giving Miller the benefit of the doubt toxic, vile, and reckless
That's not the way I interpreted his position. I think the level of detail available to use is fairly thin and many here are taking some artistic license when filling out the context mentally.
It seems to me that Miller and another boy had an extremely abusive relationship with a third boy over an extended period of time. This culminated with a disgusting and violent assault, which led to criminal charges against Miller and his counterpart when they were 14 years old.
At some point in the process, Miller's counterpart apologized in-person to the victim and the victim's family. The family has since expressed that this had at least some positive impact, or if nothing else, was a gesture that indicates at least to some degree that he's more remorseful than Miller.
It's not clear whether the in-person apology happened before or after the court ordered that the bullies offer written apologies to the victim and his family. But it seems Mitchell's only apology was in the form of this letter, which the victim's family claims they never even received.
According to the victim's family, after the incident involving criminal charges, Miller continued to exhibit some behaviors which they interpreted as taunting in nature. They have noted that this behavior, and the lack of an apology leads them to believe Miller is not remorseful. It seems the official responsible for their sentencing also singled Miller out as not remorseful.
Some unknown period of time elapsed after the alleged roller-blading incidents and a time period in which Miller points to as the beginning of changes within himself which have led to his no longer considering himself a racist bully. Officials with the Tri-City Storm, the University of North Dakota, and the Arizona Coyotes have all noted that Miller has changed and is no longer a risk to behave in the ways that led to his previous crimes.
It's possible Miller spent his entire 15th year with a worldview similar to his 14th year. It's possible Miller didn't begin making the changes necessary to grow beyond this until he was sixteen or nearly sixteen. It could be the changes seen by hockey officials after this time are what they've noted when asked. It's possible that this was too little, too late in the eyes of the victims who were never given an apology earlier in the process, when the assault was more recent.
It's also possible Miller is just lying about these changes, and feels no remorse for his actions, and is only saying what he thinks he needs to say to help his hockey career. It's also possible these hockey teams are essentially doing the same thing; saying whatever they think will allow them to add a good player, while limiting negative perception as much as possible.
Anyone could fill in any of that with whatever bias, projection, or imaged context they want. It's easy enough to invent reasons why Miller is even worse than he's being portrayed and deserves no opportunity ever again or that he's actually much less of a villain and should be given an opportunity to prove himself.
So far, what I've been able to piece together is a pretty small picture. I think Miller did some really nasty things to another kid for an extended period of time, right around Middle-School/Junior High/Secondary School. I think his partner in crime apologized in person and Miller didn't. That strikes me as a really bad sign. As does the victims and the judge singling him out. I don't know if that's because Miller got a much later start on his path to self-improvement, and the victims and the judge are going off of old data. Or whether it's simply because Mitchell has only offered lip-service when it has been convenient and suited his own interest. I don't know whether he's lying or not. And I don't know whether Tri-City, North Dakota, or Arizona actually care whether he's lying or not. I suspect they do care, and I suspect they believe he's not lying. But they could easily be wrong. And so could I.