Ethnic discrimination

Your German client is very radical and is an activist against all types of racial
and ethnic discrimination. He is about to fly to the U.S. to further his agenda. He has
prepared a speech which he intends to present at a protest at the Lincoln Memorial in
Washington, D.C. In the speech, he will demand that American blacks receive
reparations from the U.S. Government for slavery and will advocate an eventual terror
campaign by blacks if the reparation demands are not met. He then plans on marching
through the residential areas of Georgetown, the Washington neighborhood where
government officials live, with an amplified megaphone at 3:00 a.m. to shout his
demands. He also wants to enter the halls of Congress in chains during a time when the
Capitol building is open to the public as a symbolic protest against the failure to pay
reparations. Can the government restrict these forms of speech?