Making neighbourhoods your property and removing undesirables for trespassing is illegal. This is primarily so the IRS can make more money. The other effects are also government-friendly.
If you can only exclude undesirables by paying more than they can afford, all desirables must get high-paying jobs to avoid especially shitty grass monkeys. Indeed it's an arms race to get the highest-paying job, higher than the slightly-less-desirables, so as to lock out as many undesirables as possible. The IRS is made very happy, because anyone who prosecutes them for corruption will get cut off from the taxation hog trough.