I agree that Mel Gibson & Danny Glover belong on the list. Yet, regarding the _Lethal Weapon_ movies, the antigun messages splattered through them are the work the director Richard Donner (who is on the list). Donner has a long history of antigun agitprop going back to his work as a TV director in the early 1960s.
For instance, for the old _Fugitive_ series, Donner directed a blatantly antigun piece of trash episode about two 12 year olds who order a rifle through the mail (as Oswald was alleged to do) and stir up trouble in their little town as they try to capture Richard Kimble with it. Of course, Kimble gets away. The story ends with one character, a law enforcement officer, making a speech how buying guns this way should be illegal. It was soon to be. The title of the episode of is "In a Plain Paper Wrapper." It first aired 19 April 1966. (Source: IMDB.)
Note the year 1966 was the first time the Congress seriously approached voting on the law the would become the Gun Control Act of 1968. I doubt it was a coincidence that as the proposal was before Congress in 1966 that the antigun hooligans took to the airwaves with their propaganda through the guise of entertainment. It is for this reason the NRA list matters. Some of the people on it may be has-beens, but they reflect the reality the entertainment industry is no friend of the 2nd Amendment.