Claiming the ACLU is a communist organization is saying that upholding our constitutional rights is a communist plot. It's good to know that "conservatives" think the Founding Fathers were communist agents who wanted to set up a Stalinist dictatorship. It's also good to know they see the US Constitution and Bill of Rights as evil communist documents.
The ACLU is involved in political issues by its nature, since it is designed to stand up for and protect individual rights and freedoms, but it is not aligned with any specific political party or message and has nothing to do with communism, which is an economic system. The ACLU reviews cases where rights are violated either individually or by law and stands up for the people in order to get the situation rectified, regardless of political party or belief.