Their biggest target is the mythical wall between church and state. They absolutely reject the notion of anything Christian in the public sphere, but they defend the right of children to view pornography in public libraries. They have no problem with homosexuals starting a recruiting group on a junior high campus, but blanch at the thought of a Bible study on that same campus.
Their perversion of the First Amendment has become so accepted in common law that people don't understand that it has no historical basis whatsoever.
Never do they defend a conservative cause. It is perfectly acceptable for children to be taught about Islam in public schools, because Islam is destructive to the West. When people are robbed of their guns by overzealous "law enforcement," the ACLU is oddly silent. They didn't say a word about the murders at the Mount Carmel compound in Waco, Texas. They don't say a word about the McCain-Feingold Free Speech Suppression Bill that was passed as "Campaign Finance Reform."
If you would trust the ACLU to safeguard your constitutional rights, you'd trust Bill Clinton to babysit your teenage daughter.