There are two clips on this subject, both from DailyKos. Here’s the first, heralding the National Labor Relations Board action against Walmart for — what else? — the way it treats its workers:
Daily Kos: Labor board charging Walmart with illegal threats and firings of worker activists.
And here’s the second, which really illustrates the first (it’s a photograph) and could be presented as evidence in any court:
Daily Kos: If You Aren’t Sure Walmart Needs to Pay Higher Wages, This Photo Will Erase All Doubt.