Gilbert called James "disloyal" and labeled his decision a "cowardly betrayal" hours after he appeared on national television to announce he would join the Heat.
"I don't regret it. I think that's the feeling that I had and most of Cleveland had. ... I can't back off on that," said Gilbert, who joined "The Really Big Show" with Tony Rizzo on ESPN 850 WKNR in Cleveland on Wednesday morning. "That letter was to the fans and the supporters of the Cavaliers and it wasn't to the player that left, it wasn't to the rest of the world. It wasn't to anybody but them. I wanted them to understand not only how I felt but how everyone felt in the entire organization."
Gilbert has not talked to James since: "No. I didn't even talk to him before, as you know."
Gilbert threatened in July to reveal more of James' negative behavior when he was with the Cavs. He has since changed his mind.
"Emotionally at first ... you kind of want to dump anything and everything for five years that you didn't like," he said, "but in reflection, for me to bring some of that stuff up now would be like sour grapes."
Not long after posting the infamous letter on the Cavs' team website, Gilbert told The Associated Press that he felt James quit during last season's playoffs against Boston.
Gilbert -- whose comments drew a $100,000 fine from Commissioner David Stern -- didn't take back those remarks, either.
"There are some of the things everybody has to make their own personal judgment on," Gilbert said. "It's a subjective judgment when you watch a game or watch a tape. You make those kinds of judgments. I'd rather not answer directly. I'd really rather not comment what my feelings are any more, but everybody has to make their own decisions on that."
Gilbert has taken a low profile since July, when James left the Cavs after seven seasons. James' decision caught Gilbert by surprise because in the days leading up to his announcement, the 25-year-old maintained re-signing with Cleveland was still a possibility.
Gilbert felt betrayed by James and was upset that the All-Star forward did not communicate his intentions to the team until an hour-long TV special to announce his decision was already on the air.
In his letter to Cleveland fans, Gilbert not only ripped James but he guaranteed his team would win a championship before his former player.
He still believes that's possible.
"You never know," he said. "Look, these things will play themselves out and we'll see what happens. It was certainly something that put more emphasis on the future and put more pressure on everyone here to say, 'Hey, let's deliver as smart and efficiently as we possibly can.' We'll see what happens."
Now, Gilbert said, he and the Cavs are motivated to move forward without James, whose Heat opened the season with a loss to the Boston Celtics on Tuesday.
"That was sort of a surreal experience ... I guess they are only going to be 81-1 now," Gilbert said.
The Celtics visit Cleveland on Wednesday night.
"[Our] entire franchise is very motivated for a lot of reasons," Gilbert said. "No. 1, we just want to deliver that championship to Cleveland, which we've always said is our main mission and goal since day one. I would say that ["The Decision"] is probably putting a little lighter fluid on the motivational fire."
In the days after James' departure, Gilbert was accused of coddling and enabling the star. Critics said the preferential treatment given to James and his inner circle of friends empowered them into thinking they could get away with anything.
Gilbert said there are many misconceptions about what went on.
"There's a lot of nonsense that LeBron was asking for all these things and doing all these things and having all these privileges," said Gilbert, who acknowledged watching James' debut with the Heat on Tuesday night. "It's simply not true. None of that stuff happened, none of his friends flew on the plane. It's simply not true.
"In respect to him, he didn't ask for huge material things. There's some people that had some tickets before we got here, which we honored the five years we were here, but there really wasn't that much stuff. People write about this in the big-picture sense, but you never hear what the details are because there aren't any."
Among his many accomplishments with Cleveland, James became the leading scorer in franchise history and carried the Cavs to their only NBA finals appearance in 2007. It's assumed that some day James will have his jersey retired by the team and hung from the rafters of Quicken Loans Arena along with those of Austin Carr, Mark Price, Larry Nance, Brad Daugherty and others.
Gilbert sidestepped a question as to whether he would ever honor James by retiring his No. 23.
"We haven't even had that discussion on any player," Gilbert said. "I would assume that it's something you would do when a player retires. It's something that we haven't addressed. I'm sure it will come up and as it comes up, we'll address it."
Information from The Associated Press was used in this report.