Berzerker
Deity
As Lexicus pointed out sometimes it's a useful tool like in the Civil Rights Movement. Boycotting also helped end Apartheid in South Africa when people joined a BDS style movement against South Africa.
This is about getting people fired over free speech, not ending Jim Crow. Your analogy equates the two. Cancel culture attacks on free speech were essential to maintaining Jim Crow.
If Roseanne had made a racist and bigoted slur about an African American on Twitter I doubt "but I'm an Obama supporter" would have helped her much. The only difference is fewer right wingers would be jumping to her defense.
Barr didn't know Jarrett was black, her comment about Planet of the Apes referred to a resemblance to Kim Hunter's hairstyle.
If you don't have either truth and merit or talent on your side it might be a good idea to be careful how you use your freedoms.
Free speech is ailing if comedians should be careful. When I was a youngster it was the socially conservative and fundamentalist crowds telling comedians to be careful. But Barr was right (truthful) about Jarrett, she looked like Kim Hunter's character. Other people made it about race, people who didn't like her because of politics.