Frankly, it may all be a result of the Heller decision. Prior to Heller, the prevailing theory among legal scholars was that 2A was a collective right, not an individual right. Never agreed with that theory personally, but every Constitutional law professor I've come across in my career has held that position. After Heller, the Supreme Court has expressly held that it is an individual right. The ACLU has long held themselves out as being the one true defender of individual Constitutional rights. Heller dropped 2A in their laps. Glad to see they have (at least in this instance) been true to their stated mission, regardless of conservative/liberal or right/left politics. What I would be interested to see is how their liberal base responds to this stance on 2A...