The 76-year-old Dr. Kildare star revealed his homosexuality in his autobiography, Shattered Love, published in 2003.
Rumours about his sexual orientation had circulated for years, but he refused to discuss them over fears work would dry up.
Now he admits the confession wasn't a good career move - and he's advising young gay stars to stay 'in the closet'.
He tells The Advocate, "There's still a tremendous amount of homophobia in our culture. For an actor to be working (at all) is a kind of miracle, because most actors aren't. So it's just silly for a working actor to say, 'Oh, I don't care if anybody knows I'm gay' - especially if you're a leading man.
"Personally, I wouldn't advise a gay leading man-type actor to come out... Despite all the wonderful advances that have been made, it's still dangerous for an actor to talk about that in our extremely misguided culture."