My son, 8, was upset that some of his friends at school were bullying another friend. He didn't know how to deal with it. I wanted my son to see that there is a way to stand up for people, respectfully, peacefully, and bravely. We watched this movie together, pausing many times to discuss situations. We ended up talking all evening, with my son opening up about all sorts of thoughts. He's usually very quiet, but he was very inspired by Ghandi. It's not just history... Ghandi shows principles that we can all use to stand by our values while respecting and even befriending those who disagree. This movie showed this perfectly. I remember first watching it when I was twelve, and was also inspired. Watching this with your child can be a great way to open up a discussion about respect, conflict, values, and/or bravery.
I would not recommend letting a child watch it alone, as it can be hard to follow without explanation, and the theme could get lost.
There is some violence that is upsetting, but I think the value of the message and the history make this violence appropriate to its context. Violence is not overly dramatized or promoted.