Joe Yanny told The Associated Press that allegations of marital infidelity against James and the ensuing media "feeding frenzy" have ruined the biker businessman's life.
"This whole thing has destroyed Jesse's entire universe," Yanny said. "Right now, he's a broken man."
He said James is still in love with Bullock and hopes the marriage can be saved.
James checked into a rehabilitation center after weeks of reports that he cheated on Bullock throughout their marriage. Yanny declined to say what James is being treated for, but said people shouldn't assume it is for sex addiction. He also wouldn't rebut specific allegations lodged against the West Coast Choppers owner or say whether there are plans for the couple to get a divorce.
"The allegations back and forth about what happened - those are private matters to be resolved between a husband and a wife," Yanny said. "It's not appropriate for a public airing."
He said the vast majority of stories about James are untrue.
"Jesse is in love with Sandra," Yanny said. "The single most important thing to Mr. James and the children is that the marriage somehow survive."
James and his camp have said little since a woman told In Touch magazine that she carried on an affair with James while Bullock was shooting the blockbuster hit "The Blind Side."
The film earned Bullock widespread acclaim that culminated with a best actress Oscar. Within days of her win, the cheating allegations broke and Bullock withdrew from the public eye.
James released a statement saying he had used "poor judgment" and deserved "everything bad that is coming my way."
Bullock has not spoken publicly about the matter, and her publicist did not respond to e-mailed questions for this story.
Public support for the actress has remained high as more women have stepped forward claiming they had affairs with James in recent years.
Bullock and James met in 2003 and were married in 2005. It seemed like an odd pairing - the Hollywood actress often called "America's Sweetheart" marrying the tattooed biker who designed custom motorcycles and starred in reality shows such as "Monster Garage" and "Jesse James is a Dead Man."
Yanny blasted media coverage of the case, saying the privacy of Bullock, James and his children had been repeatedly violated.
"It's nothing but voyeurism at this point," he said. "Enough is enough."
He said the coverage of the story was overblown and that it lost its newsworthiness long ago. He said he is concerned about the media continuing to pursue James' children and family while the 40-year-old is undergoing treatment.
"There are many more significant things in the world that people ought to be talking about and delving in to," Yanny said.
He acknowledged James has made many mistakes in his life, but that he has also quietly supported numerous charities and his various businesses have created many jobs and opportunities for others.
Yanny said he expects James to persevere. "He certainly will come out of this a better man," he said. "I hope he comes out of it with the things in life that he cherishes."