It's the interpretation of the second amendment by SCOTUS that has been inconsistent over time, not the ACLU's position. Collective/militia rights is a widespread interpretation of the second amendment (which the ACLU holds). Interpreting "right to bear arms" as unrestrained individual gun ownership is not the default position just because modern NRA advocacy says it is.
This isn't responsive to Rayiner's point. "Why" the ACLU doesn't expansively support the right to bear arms the way they do speech and freedom from search is interesting, but doesn't rebut Rayiner's point "that" they don't.
You're painting their position with a brush the size of a small planet. Here's their actual position, which is for Constitutionally-consistent gun regulations and against proposed gun regulations which raise civil liberties concerns: https://www.aclu.org/blog/civil-liberties/mobilization/aclus...
This article approaches gun regulation from the standpoint that the 2nd amendment mostly doesn't exist. It's arguing that the regulations should be consistent with the equal-protection clause. That's basically in-line with what rayiner said: the ACLU doesn't care about the 2nd amendment, and only defends gun issues when they touch other constitutional issues.
Has the ACLU's stance on the right to bear arms has been inconsistent, as in, changed quite a bit over time? Or they just haven't had much of a stance to speak of? Honest question.
In 1991, they believed it was an individual right. Now they believe it's a collective right. I don't know of any major cases the ACLU brought on behalf of gun owners (but probably wouldn't know if they had).
I can't speak to that - but they also haven't felt as much of a need to devote resources to it as they feel, accurately, I believe, that the NRA has enough resources and a loud enough voice on that topic.