When Proctor has been pushed to his limit, having failed to convince Danforth that Elizabeth is innocent and that Abigail has led the town to commit greats sins by condemning people with lies, he lashes out at Danforth and the court. 

Proctor: laughs insanely, then: A fire, a fire is burning! I hear the boot of Lucifer, I see his filthy face! And it is my face, and yours, Danforth! For them that quail to bring men out of ignorance, as I have quailed, and as you quail now when you know in all your black hearts that this be fraud—God damns our kind especially, and we will burn, we will burn together!

The court maintains its position that “the voice of Heaven is speaking through the children” and refuses to accept the truth of Protor's claims. 

These quote is important because it demonstrates 1) Danforth's guiltly involvement in the witch-trials (as he is dedicated to promoting his own power even if that means killing people under false pretenses) and 2) even strong people like Proctor cannot defeat the force of the majority (or the leaders of the majority) as long as the majority remains unmoved.