Off screen behavior can absolutely be related to the more extreme ends of method acting. Some method actors, not all, literally stay in character after the camera stops. I am being very careful to not cast my opinion on all method actors because there is a spectrum.
And I don't fully subscribe to separating art form the artist If they're alive and still being intolerable human beings, I think it is correct to incorporate that into overall valuation of their skill as an artist. The creative process is as much a part of the art as the end piece is.