How did Miller show how bad Puritans were? How does this connect to the Red Scare?
I think that there are two issues in the question. I am not entirely certain that Miller "had it out" for the Puritans and solely wanted to show them as "bad." Rather, I think that Miller is seeking to show what happens in any social order where there are no limitations to external encroachments. When there is no institutional safeguard to check abuse, bad things tend to happen. For example, in Salem, when one was accused of being a witch, this ended up being the most damning of indictments. There was no due process, no individual rights to representation or speech, no full embrace of procedural jurisprudence, nor any means for individuals to seek redress for decisions. When a social, legal, or political system is predicated upon absolutism- what says goes- problems arise. The fact that so much power is placed in Abigail's accusations is where Miller seeks to explore and create discourse. In much the same way, the HUAC hearings of the 1950s, where good people were accused of being "Communist," in a manner where the mere accusation destroyed lives, families, and people, there were few, if any, institutional safeguards to help protect those individuals who had to endure such public "shaming." Miller is seeking to bring out that any order where silence and obedience is the norm as opposed to discussion and debate has a greater tendencies for more "bad" things to happen than good.