In some ways these marches are good. It gets people out of the house, into the fresh air. They get to meet new people in a social situation.  Unfortunately, it's so crowded in some of these places that there's not much room to actually "march", so the people really don't get much exercise out of this event.  And Washington D.C. is a dangerous city for anyone who is unfamiliar with which places to stay away from (high level of violent crime).  So getting exercise by walking around on their own could be fatal for some of the demonstrators.