I don't think you deliberately overlooked the other instances of "liber", though if you're a programmer of moderately high caliber, you could fairly easily look up all words that contain "liber" (if you're in the habit of liberally applying your programming skills).
Also, the above sentence contained three instances of why you don't want to (and didn't look that contrived), although I'm pretty sure you have to be deliberately looking for them.
Sorry, you're correct at least insofar as I should have said ^liber[a-z]*
The adverb "liberally" will be a casualty since it's a homonym for the politically charged version I'm trying to avoid.
I'll grant that "liber" and "liberate" also fall victim here, but I would be surprised if it was hard to rephrase either of those in almost any conversation.
An article from the Wall Street Journal. The original title might be slightly mind-killing for some people, but I found it moderately interesting especially considering that many LessWrongers formed part of the data set for the study the article talks about and a large fraction of us identified as libertarian on the last survey.
Inside the Cold, Calculating Libertarian Mind
The original paper.
Understanding Libertarian Morality: The Psychological Roots of an Individualist Ideology