It's "Bad" because that sort of product dumping causes an unhealthy addiction as well as the investment of your wealth into the wrong areas...
...For the same reason that dope pushers give away that first free sample, to get you hooked.
Well, that's what robber barrons and monopolists have done throughout history; they've been willing to endure short-term losses in order to gain a long-term lock on a Market.
Whether you are talking about railroads in 1900 or Standard Oil in 1925 or AT&T in 1950 or OPEC in 1975 or China in the 2000's, they were (and China still is) willing to lose money in the short term to gain or maintain their absolute monopolies for the long-term.
China is essentially dumping their goods on us right now, but our anti-dumping laws can't touch them because the laws didn't cover currency manipulation back when they were written. By dumping their subsidized goods onto the Market, no one else can compete with them...driving their competition out of business.
That's not capitalism. That's direct foreign government intervention into global economies to the tune of more than $195 Billion per year in currency manipulation expenses.
Of course, such low-cost goods are addictive. To the consumer, anyway. Everybody *wants* lower cost products just as the dope junkie wants another high. But that doesn't make it right, and it certainly isn't healthy for us or our long term economy.
Though granted, it's a lot of fun in the short term.