However, Johnson also said the board of CBS owes Moonves and the alleged victims a "quick" investigation, acknowledging that Moonves has already admitted to making women "uncomfortable" by "making advances."
"I do not know of a ... finer gentleman or more dynamic CEO than Les Moonves," said Johnson, who called Moonves a "great friend" and said he's known the CBS chief for more than 20 years.
"My only advice to the board would be that ... whatever they want to do to get the results of their investigation to do it quickly," Johnson said in an interview with CNBC's "Closing Bell." "That's fair to Les, that's fair to the people who made the allegations, and it's fair to the shareholders."
Johnson spoke after CBS announced the board would hire an outside counsel to conduct an investigation on accusations that Moonves had sexually harassed female employees.
Those allegations came in a New Yorker magazine article Friday, which cited six women. In a statement, the 68-year-old Moonves said he regretted making some women uncomfortable but that he abided by the principle that "no means no."
A statement from the company to The New Yorker said, "CBS is very mindful of all workplace issues and takes each report of misconduct very seriously."
Johnson, the nation's first black billionaire, said the CBS investigation is much bigger than the company, adding corporate America as a whole will need to decide how to best handle allegations of sexual misconduct.
"How do you determine the level of accountability if the allegations prove to be correct?" Johnson asked.