No matter how unsightly or disgusting. The answer is, nowhere. Serious political protesters as well as full-time vagrants and others whose hold on reality is perhaps less firm than yours and ours, have every right to express their views, through carrying signs and leafletting. In appropriate places, such as on the Ellipse, in view of the White House, for a limited number of hours. Anything beyond this is tyrannizing the rest of us.
Demonstrators have no right to deprive thousands of park visitors of a nationally significant sight.
Defacing the White House and Lafayette Park is not the expression of free speech. It is a damned crime. And we can only pray that this administration and the Supreme Court have the guts to call it that.