It does not subsidize viability of businesses, because the requirement that businesses have to "pay their own way" by taking responsibility for the entirety of their employees' living costs (and not just the externalities) is a fallacy. Your math only shows that all the businesses in a society have to pay enough that the living costs of every member of that society are covered (or else that society will go down the crapper real quick). It doesn't follow that businesses have to pay out every employee's living costs individually; the first condition can be met even if the costs are distributed.
I'd like to turn your question around and ask, why shouldn't paying some employees less than their living costs be a viable business model, if the business pays enough to cover its own externalities and is otherwise ethical.
Because it is ultimately acting as a drain on other businesses, which have to pay the amount it isn't providing. That makes them less profitable, and makes the area less attractive and less condusive to setting up such businesses. It's bad for exactly the same reason that any other business subsidy is bad.
If you can come up with a reason why business A should have to pay the expenses of the employees of business B, I'm all ears. But in the absence of such a reason, it's reasonable to call business B a mooch.
The mistake you're making is assuming that the alternative to WallMart paying below minimum wage is unemployment.
It's not only about Wal-Mart that has a profit margin to be viable anyway, but also marginal businesses who don't have that luxury.
If that really is the issue, then there is no reason why you wouldn't agree that WallMart is being a mooch. Then we can deal with those other businesses separately.
Any time you wish to start offering facts into evidence to support your contention that failure to pay enough for "decent safe housing, decent safe food and decent safe healthcare" implies you're a moocher and a leech, knock yourself out.
I've offered plenty. You've not replied.
The mistake you're making is assuming that the alternative to WallMart paying below minimum wage is unemployment.
No, the reality is that when you eliminate a bad job a good one doesn't magically take it's place.
Nor do magic pixies magically gun down your former customers to magically stop them shopping elsewhere. In practice, the closure of a burger joint or a grocery store, or any other FMCG outlet (Fast-Moving Consumer Goods) doesn't do much to reduce the demand for the product. You close a several thousand square foot superstore, then someone, somewhere, will do more business as a result.
If you disagree, and think that all minimum wage businesses will just close and none of those jobs will just disappear, then we can discuss that, but you'll need some kind of reason for thinking that will be the outcome.
And even then, all it proves is that those businesses would never have been viable without subsidy, because you're claiming that neither they nor anyone else can run a business in that niche without one.