That Avast post-mortem made me smile. I think they did a great job, not only explaining in clear language what happened, how users can help with reporting similar cases, and the final shout-out to TextSecure is the cherry on top.

On the other hand, TextSecure's blog post starts and ends with a "Avast is evil and sucks" vibe (in the original pre-update post). It's understandable, they're a starup and probably panicked a little. Still, if you leave the post mid-read you get a bad image of Avast.

I'm not familiar with US law, or generally litigious, but surely you could sue for damages, particularly so given the public statements on top of the false positive.