The founders of the US started a war that killed tens of thousands of colonists over small taxes and a desire to eventually end slavery, which was basically unprofitable at that point in America. The local connected and rich people thought those were valid reasons for political violence.

The "Boston Massacre" involved a crowd of people throwing rocks and balls of ice at soldiers and getting shot at.

But now it's all "Oh political violence must be avoided at all costs". Now it's "Political violence doesn't work, now lets set off fireworks on July 4th to celebrate the birth of our nation through violence"