Not that I agee with the US court’s decision, but I’ll quote from it all the same.
Oberwetter’s expressive conduct occurred in the interior of the Jefferson Memorial, not
on the sidewalks or parkland surrounding it. And the physical characteristics of the Memorial’s interior indicate that it is a nonpublic forum. It is physically distinguishable from the surrounding parkland: an individual must affirmatively decide to visit the interior of the Jefferson Memorial. The visitor must step off of a path, ascend forty steps, and traverse a portico – passing a sign requesting “Quiet Respect” – before entering the Memorial’s interior. Unlike the sidewalks at issue in Grace and Henderson, the pedestrian is inevitably aware that in moving from the parkland to the interior of the Memorial he or she “ha[s] entered some special type of enclave.” Grace 461 U.S. at 180. A pedestrian simply does not “happen” upon the interior of the Memorial…
Wheras the russian memorial coulde be seen only in the background.
Moreover, the Jefferson dancers were arrested and held for a few hours, not sentenced to spend fifteen days in jail. Deplorable but not necessarily comparable.