‘The OC’ actor has made a career out of playing sleazebags, from an adulterous lawyer in ‘Sex Lies and Videotapes’ to the Donald Trump-inspired real estate mogul Buddy King in ‘American Beauty’. As he appears on Broadway opposite Julianna Margulies in a new play by Delia Ephron, he talks to Tom Murray about the curse of good looks, absconding on set with Peter O’Toole and why celebrities have as much right to talk about politics as anyone else