Very interesting that they chased you out of Lafayette Park. If was for a “violation” of 36
CFR 7.96 (
https://www.law.cornell.edu/cfr/text/36/7.96). specifically G.2 (u need permits) and the size of group that needs a permit, note that the people counted are those who are “in” the “demonstration”, not those who are “drawn to” the demonstration. (see the definition in G.1, an event is a demonstration only if it draws onlookers, or is likely to.)
The crowd in Lafayette Park when Osama bn Laden was shot was not treated as a demonstration, or a celebratory event.
http://jacksonville.com/sites/default/files/imagecache/superphoto/050211BinLaden3.jpg