Stephen Crane begins with the brutal Old Testament warning that God’s anger will punish children for their parents’ sins across several generations. The speaker turns that logic inside out, speaking to a “picture” — likely a religious image of the judging deity — and calling it unrighteous, wicked, flatly hating it. This isn’t personal hurt so much as a surge of protective fury for the helpless. The speaker then dares this vengeful figure to go ahead and smash the heads of “those little men / Who come blindly.” The final line — “It will be a brave thing” — drips with sarcasm. There’s no courage in hurting people too unaware to even know why they suffer. The mood is defiant, sardonic, and bleak. Crane gives us a speaker so revolted by inherited punishment that he flings his contempt directly at the source, challenging it to show how “brave” its cruelty really is.
"And the sins of the fathers shall be" — Summary
"And the sins of the fathers shall be visited upon the heads of the children, even unto the third and fourth generation of them that hate me."
Well, then I hate thee, unrighteous picture; Wicked image, I hate thee; So, strike with thy vengeance The heads of those little men Who come blindly. It will be a brave thing.