Why do conservatives defend McCarthyism and the Red Scare?

I know this sounds like a stupid question but there was someone in my cl two days ago that raised his hand and said that McCarthyism was 'essential to building trust back into the government and bring the people together against a possible communist threat at home' I'm just paraphrasing what he said but why did he say that? Do conservatives really think that persecution under McCartyhism is a liberal interpretation of whitewashing history?