Okay kiddo, anti anti-communism means you don't like people who don't like communism. It's like if you really like ice cream and someone says they don't like ice cream, you might not like them because they don't like something you really enjoy.
Similarly, people who are against communism (anti-communists) don't like it because they think it's a bad idea or it's not fair. But anti anti-communists don't like the people who don't like communism because they think everyone should be allowed to have their own opinions and beliefs. They don't think it's right for someone to tell you what you can or can't believe.
It's like having different favorite colors, some people might like pink while others like blue. It's okay to have different preferences and beliefs, and we should respect each other's choices.