There are studies that suggest that huge companies, like Wal-mart can contribute to poverty. The correlation is so high, the amount of Wal-marts in an area can predict poverty levels. The reason for this is because huge companies, like Wal-mart often don't allow their workers to work full time in order to avoid paying higher taxes and avoid giving their workers benefits. These same people who are underemployed are also usually working at minimum wage. This means that huge companies can have a negative effect on family wages. Lower family wages can mean less spending in local economy..Which can be devastating.
If employers are held to a quota for full-time workers, it can help remedy this situation.
It isn't your business, it isn't your risk, it isn't your money. If you feel like people should be able to get full time employment, you start a business, you risk your money, you put up with the regulations on everything involved in business and then you maintain full time employees.
Business is in business to make money, if that means part time workers - look at what is the incentive to do that, remove the government's meddling and companies will hire full time workers (they cost less to maintain the several part time workers)