I wouldn't actually mind as much if he had admitted it in his interview. He could have said he didn't check his mirrors and was sorry for impeding Jenson. But not only did he not do that, he lied about an imaginary car being infront of him..
Now maybe I have it wrong, but I'm 93% sure that Massa didn't have a car immediately infront of him to justify the slow down, where as Button discovered some Italians had built a big red blockade in the middle of Monaco..
Traffic, Owenb, is different to blocking on the last corner of a hot lap for the person behind with an easy step to the right side of the track where the pit entrance is to let him through. Traffic was inevitable and we're not saying people didn't get in the way on laps, but no one else appeared to have made such an avoidable block at a critical point. It still would have been a harsh penalty, but I think Ferrari dropped the ball on not informing Massa correctly, or Massa dropped the ball on not looking in his mirrors.
I would have no problem giving Massa a penalty for what he did if he had cost Button a position on the grid. What I disagree with is the blanket-If he impeded someone then he should get a penalty regardless of whether it cost the other driver a better position. I am going to repeat myself here but hopefully the stewards, whom include Damon Hill, used some common sense and looked at Buttons lap and saw it wasn't any better than his fastest lap.