Everyone who makes a purchase at Wal-Mart does so voluntarily. Everyone who works there does so of their own free will. The only potentially coercive element in Wal-Mart's business practices are the various "packages" put together by state and local governments to entice Wal-Mart to build stores, which are paid for by taxpayers (and, that's very presumptive on my part; I actually don't know if any such packages are routinely extended).
Anyone who attacks Wal-Mart for paying low wages, utilizing part-time employees, not offering healthcare benefits, driving out smaller businesses, etc., etc. is attacking the very essence of a free society. That is, they attack the ability for individuals to make decisions for themselves--to shop at Wal-Mart and to work there. In doing so, they attack the concept of individual rights at its roots.
One of the more specious arguments against Wal-Mart is that, by not offering healthcare benefits, they push workers into public healthcare. It's fascinating how it is only in this context that so many people discuss the fact that such healthcare is paid for by the rest of us; usually, this fact is ignored when the same folks call for expanding government-provided benefits like healthcare. Of course, in a truly free society, everyone would be responsible for their own healthcare, but such a discussion is beyond the scope of today's post.
A more valid argument could be levied against Wal-Mart for its practice of purchasing so many producs from China. Even this, though, isn't clearly negative. First, the economic impact for the US is positive--we're able to purchase goods at much lower prices, thus freeing up resources for spending in other areas. Second, ultimately, such trade chips away at communism, and improves the standard of living of the Chinese people. Eventually, Chinese wages will rise as their economic conditions improve and their expectations increase, and China will no longer be competing purely on the basis of lower wages.
The attacks against Wal-Mart are a fascinating look into the Left's attack on capitalism in general. Unfortunately, such attacks seem to be getting more common and more aggressive. The Left seems to be more confident for some reason, and that concerns me a bit.