//...protesting is part of a healthy democratic society.//
It is if it does not effect people who have no interest in the cause. If it does effect them it is an imposition undertaken by one lot of people intent on pressing their cause over another. There's plenty of ways people can protest without gluing themselves to trains and roads. If they just want to roam around with placards whilst not interrupting others going about their business, that's fine. But most protesters are not content with that.