I am not the kind of person who can talk people into emotions, but I can say this:

Les Miserables is about tragedy, hope, and love, and I don't find it manipulative because I give myself over to it gladly, wallow in catharsis, and emerge with a renewed sense that "even the darkest night will end and the sun will rise". So that's some of why I love it, I guess. But that's me -- I can't make anyone else feel that way.