That's how socialism is defined, that the interests of society come first.
You can’t go to the socialist stock market and sell 5 shares of your “ownership”. You can’t transact it. If you don’t like the product, you can’t choose to buy a different one.
I like good definitions, though, and the GP was pretty sloppy about his terms.
"is the oldest con in the book"
Con? In one sense, yes. It does not bring about the promised prosperity. Attempts at socialism generally fail, and I believe the incompatibility of such system with human nature is fundamental.
It is not a con in the sense that they actually mean it seriously and want to implement it, though. If a socialist politician talks about expropriations and nationalization, you'd better believe that this is his actual intent. History says that this intent was acted upon many, many times.
My understanding of socialism is that, in practice, it is merely the assertion that some choices about how labor is allocated should come from democratic decisions instead of the market.
Only a mixture of capitalism with socialist policies can be beneficial to man, if you go with absolutes it brings misfortune to most people.