Because the communist agitators who form and operate the protests instigate them? Every one of the large so-called "peace" groups around today was formed by either Workers World Party, Communist Party USA or the Revolutionary Communist Party. Each has their own "anti-war" front group. WWP (aka, Party For Socialism and Liberation) has as their front groups, ANSWER, Troops Out Now, FIST. CPUSA has a huge front group as well: United For Peace and Justice, also Peace Action. The RCP has the slimey mainly youth-orientated "World Can't Wait". None of these are really anti-war. They are pro-revolution. They worship mass murders such as Mao, Stalin and Che. They support murderous regimes such as North Korea. They support bloody leftist uprising wherever they take place. One can hardly be a pacifist and support these things.
“One can hardly be a pacifist and support these things.”
Yet pacifists line up to participate. Pacifists are socially retarded. That being my point, and well backed by your post I might add.