Here in America, we are allowed to express our disfavor with the current political regime by protesting in "free speech zones" thoughtfully arranged for us at public events where the President will be attending. These "zones" are conveniently located far away from the actual events. This is done for the safety of the protesters as we would not want something "bad" to happen to them.
Apparently, due to the nature of the event, these arrangements were not made in this case, and the President was unfortunately subjected to public opinion.
HTH