Imagine you live in an apartment complex with a diverse assortment of tenants. There's a butcher, a baker, and a candlestick maker. A doctor, a lawyer, and an Indian Chief. A truck driver, a dentist, a mortician, a schoolteacher, and a mechanic.
Anything you need, you can get from the residents of your apartment. No one purchases anything from anyone outside the apartment complex. It helps to protect your apartment complex's jobs.
There's a slight problem. The schoolteacher hates kids. The truck driver is an alcoholic. The butcher is a Muslim, and won't handle pork.
Should you be allowed to trade with people who live in other apartment complexes? Even if it endangers the jobs of those in your apartments?