Coimbra is traditionally an academic city. The demonstrators were very peaceful. Had they done this in Porto, for example, it could've earn them a beating.
Portuguese peope are very good hosts, but you don't enter someone's "home" and tell them what to do. It's one of the most insulting things you can do as a visitor. And you don't tell us to "go to Africa". Honestly I'm surprised some old lady didn't came with a broom and sweep their asses into next week.