Say it with me a few times.
It means “abuse does not take away use” or “improper use does not rule out proper use,” meaning “just because you can give an example of how something shouldn’t be used does not mean it shouldn’t be used at all.”
Why, yes, I did just read one too many articles (ie, ‘one’) about how “we” need to stop saying ____ because here’s an example of where it’s used in a way the author doesn’t like, and why.
Now, there is merit to the idea that things spoken in jest are sometimes true and folks just don’t want to say it, but the last thing our culture needs is less rueful self mockery, such as when you do something basic and are absurdly pleased, notice it, and make a crack about “adulting.”
I grew up around ranchers and farmers, my mother was a teacher, and a lot of people had degrees. (Mostly thanks to the GI Bill, but mom for example majored in something ag related.)
It is normal for people to make jokes like this. The guy who’s got an AA, if you complement, oh, the sign he and the 4-H kids just made on a local store window, might draw himself up and say as pompously as possible: “Well, I do have an art degree, you know.” The gal who just managed to make a grilled cheese sandwich that actually looks good– no crumbles, the cheese is oh-so-picturesque in how it’s stretched across the cut, lovely light and dark shading across the top– will make a joke about “and now, having mastered the grilled cheese, I shall become a french chef!”
That doesn’t mean one can’t be absurdly pleased with basic things, or that one genuinely thinks praise is deserved for basic things– and if you do find yourself dysfunctional, don’t project it out on the world at large. But a wise man once pointed out that one of the most childish things around was an obsession with being very adult.
(On a side note: I’m not obsessed with ‘changing the world’. I’m working to improve it.)