Can I put "into" after "good men"? Why did he skip "into" in this sentence?
You can! However, you will have to reword the sentence if you use "into." The sentence would be reworded to "That turns good men into cruel men." "Into" is used as a function word. In this case, it indicates the condition of the men. It is okay to omit "into" from the sentence in the video because the original sentence is considered complete. The sentence can stand on its own without the indicator word "into."