I think they were meaning more along the lines of behavioral or mental issues, since they mentioned autism. In my schooling I never saw anyone get put down because of physical disorders or differences, but it was much more common for people to get bullied when they were trying to fit into cliques that their background or behavior didn't blend well with. The kind of bullying I witnessed was like a form of signaling telling the bullied that as much as they tried, they wouldn't fit in with an in-group.