I think that, on balance, I would call Leonard Mead a rebel.
You could argue that he is not a rebel because he's not exactly trying to influence anyone else. All he does is go for walks alone. Since that's not really something that anyone notices, it can't really influence anyone.
But he is a rebel because he is acting in a way that is totally different than the way anyone else in society is acting. He is coming out of his house, trying to think for himself and do things his own way. I'd say he is definitely a rebel because he is acting in ways that are so opposed to what his society expects.