Gosh- more conspiracy theories- lovely!
It would be against the law in many cases. It is not wholy his choice if he ignores better qualified candidates for the job. A chinese restaurant. Perhaps not surprisingly full of Chinese chefs and waitresses. Waitresses- not too highly paid perhaps (on base wages), due to this not being a skilled job- i.e. one that most people could perform. So no illegality. If you put your theory forward for a black guy who was the head of a hospital (for example), it would be illegal for him to not employ the people who, under challenge and scrutiny by the courts/other experts in the field, were better as brain surgeons than the person he did employ. In a company setting, employing a complete moron friend as CFO, resulting in financial ruin would leave the person who employed them open to legal action from the owners/shareholders if a better option applied for the role and was ignored.
Before you say- I recognise that this is damned hard to prove either way. But the fact is that there are statutes relating to this (Employment Rights Act, Race Act, Equal Ops for example) to ATTEMPT to stop cronyism/rascism/sexism in the workplace. Not perfect, but it is there Captain BH.