It's a quote by Robert Heinlein. I'm curious to hear its deeper meaning.
Here is the entry for the Heinlein quotation in The Yale Dictionary of Modern Proverbs (2012), giving the context for the quotation:
Never try to teach a pig to sing; it wastes your time, and it annoys the pig.
1973 Robert A Heinlein, Time Enough for Love (New York: G. P. Putnam's Sons) 51: "...[A] fool cannot be protected from his folly. If you attempt to do so, you will not only arouse his animosity but also you will be attempting to deprive him of whatever benefit he is capable of deriving from experience. Never attempt to teach a pig to sing; it wastes your time and annoys the pig."
In context, the point seems to be that it is fruitless to try to make someone what he or she cannot be. In part, the quotation is dismissive: After all, it starts by making the subject of the attempted improvement (or protection) a fool. But in part, there is also a degree of sympathy for the person who is supposedly being improved but in a way totally unnatural to his or her own talents and inclinations. A platypus can't be taught to whistle—whether or not it is too stupid to learn how—because its mouth isn't designed to form a shape necessary to produce musical notes.
- Never try to teach a pig to sing. I wastes your time and it annoys the pig.
Some people are either unable or unwilling to learn. Attempting to instruct such people is waste of time, in spite of your best intentions.
- Never try to wrestle with a pig. You get dirty, and besides, the pig likes it.
Entering into an argument with someone who mainly employs diatribe as a debating tactic makes you angry and the other guy (in a sense) happy, without settling anything.
- Putting lipstick on a pig
Spending time "prettying up" something that is inherently ugly (if you're not another pig). (Usually regarded as a wasted effort.)
- You can't make a silk purse from a sow's ear.
Trying to make something useful or artful by starting with something worthless is often a wasted effort. (But note that I've seen hints that this saying historically has sometimes had an anti-semitic twist to it.) (Also note that there are artists who have made a career of creating art from trash, so the expression should not be interpreted too literally.)
Sounds like a more-amusing iteration of "You can't fit a round peg in a square hole", the primary meaning of which is that some tools / individuals are far better suited for a given task than others, and trying to force that individual into a role for which it's unsuited is an inefficient use of time and resources.
...Of course, there's also the literal take: teaching a pig to sing probably won't end well.
It's elitist conservative crap of the sort that Heinlein found sold well. It means that lesser beings than you are not merely educationally deprived, but are inherently incapable of ever rising to your own high standards. It makes me sad to hear Heinlein quoted at his worst.
An early Heinlein novel, Double Star, has the exact opposite ideology as its theme. An actor with little interest in politics, but something of a conservative bigot, is hired on to impersonate a liberal politician who champions respect for and political union with the Martians, who are not human. The politician has been injured. Heinlein's protagonist must give speeches during his impersonation with which he really disagrees -- but it's a job.
There's a romantic interest. The politician who was shot eventually dies of his wounds. The actor is swept up in an effort to keep the death a secret, and to pursue the dead politician's liberal agenda.
Eventually, the former actor can hardly remember what that conservative earlier self was like.
This is my favorite Heinlein, at his best.