Actually Lee's son-in-law specified that it WASN'T an unkind cut, that Burton wanted to have Lee in his film because of their established good relationship but that Burton realized the role would not benefit the film. The statement by Lee's son-in-law asked people to stop the petition because it could only hurt Lee's and Burton's solid professional relationship.
He also said that Lee has moved on to another film and that his friendship with Burton remains as strong as always.
"Some people can thrive and bloom living life in a living room, that's perfect for some people of one hundred and five. But I at least gotta try, when I think of all the sights that I gotta see, all the places I gotta play, all the things that I gotta be at"