I saw Nader in person several years ago at the Luna Cafe in D.C., which is just East of Dupont Circle. I think this must have been around 1999, before he ran for President in 2000. This was the middle of the afternoon and Nader and his friends were leaving. Nader seemed to be joking and bantering with them, so to me it seemed like he had some personality.
Is it possible that Nader has something like Asperger's? He remembers lots of facts and has odd social skills.
I would rather think that Nader comes across cold because of his fame. When you are a famous person, you are in the public eye all of the time. It's like being on stage constantly, hence the tendency to be more reserved and standoffish.
This happened to me around the time of the post-Seattle movement. You get some press coverage and all of a sudden people treat you differently. If you are doing politics, you get attacked by people all the time, which leads one to be more defensive and circumspect.
I always thought I was a personable and open guy in person, but my public persona changed to the point where several friends have pointed it out to me. One best friend told me that she thought I was very standoffish and impersonal when she first met me. I think my initial coldness to her was because I was a bit put off that a middle-age white woman was attending a black bloc meeting.
Nader is probably a complex person like the rest of us. In the big picture, his personality is irrelevant.
Chuck