The existance of other avenues of dissent is irrelevent. Americans hold an unalienable and constitutional right to free speech and assembly. Removing them from a public area where others have access purely for their political opinions is an infringement of that right.
Whatever area is provided to protesters in which to vent, is a public place, unless they are forced to protest only in their homes or in the depths of some isolated cavern.
Free speech doesn't give us the right to be heard-just the right to freely speak. Not even the President can be forced against his will to listen to us. He has rights too.