Were groups that advocated the use of violence in the 1960s justified in doing so? Why or why not?

Very few groups in the 1960s advocated violence, except the US government, in the form of military adventure, where they went far beyond advocating. A total of about 1,353,000 deaths occurred on all sides in the Vietnam war. Then there was/is the Klu Klux Klan. We need to be watchful even now. The Weathermen were a small organization and they claimed not to intend violence, but use it if “necessary.” The Black Panthers called themselves a party of “self defense.” Whether or how often individuals in the latter two groups deviated from their charters (if any) is hard to determine.

Anyway people can justify their actions of violence it doesn't mean it was justification for everybody.

People found unique and inexpensive ways to entertain themselves during the Great Depression. They listened to a variety of radio shows or took in a cheap movie. They also took part in sports, fads, or fun contests that didn't cost anything at all. The 1930s was part of a time that is called the "Golden Age of Radio."