I'm pretty sure other stars of his caliber have made similar "topic non grata" demands in order to appear. (Hugh Grant comes to mind, for entirely different reasons).
What comes to mind about Hugh Grant for me was when he appeared on Leno's show just after he was arrested for hiring a prostitute. He's introduced, comes onto the set, applause applause, sits down in the chair, and Leno turns to him and goes, "
What were you
thinking?!!" So apparently Hugh hadn't stipulated that particular subject off limits in that case.
I'm going entirely from memory, so I may have some of the details wrong.
Anyway, as you say Mika, Jake's situation is entirely different. I think celebrities often do ask that certain subjects be off limits -- their love lives or pending divorces, for example -- but those are usually topics demanding a different sort of privacy. The specifics of Jake's friendship with Heath are private, of course, but I don't think it's too intrusive to expect that he might want to say something about his friend's passing.
The media absolutely shouldn't harass him in his private life for a comment, or on his way into the funeral, or anything like that. But if he's on a talk show or a press junket I don't think it's out of line for the interviewer to bring the subject up, and I think it would be kind of odd if Jake would refuse to answer. All he'd have to say, at minimum, is something about how sad he is, how much he respected Heath, etc. And Jake seems so comfortable and relaxed in the limelight that I don't think he'd have any trouble with that.
My favorite interviewers respect sensitive topics, too. But good interviewers have to make at least a stab (so to speak) at bringing them up. I once had to interview an author who had endured an extremely painful, shocking and highly publicized family tragedy/scandal a few years earlier. I knew I had to ask her about it, and had dreaded it. She refused to answer my questions, as I'd expected, and so I dropped it. But we both knew the drill, that I had to ask, and she didn't hold it against me, as far as I could tell.