Do you have anything to substantiate that? I'm well aware of the ACLU's stance opposing the 2nd Amendment (though some local chapters have broken ranks).The name of the organization is just a smokescreen for what is a very left-wing group dedicated to a larger government (and, hence, more police, whatever they're armed with).
They have defended the civil liberties of folks from both sides of the aisle. Westboro Baptist springs to mind as one example.