If I were anything more than another grunt like you I wouldn't be posting on these boards...
But I do try to pay attention to the more extreme cases of abuse (like Walmart) and not support them. So, I do not shop at Walmart anymore. Similarly, I try not to buy Hormel products (although they've got a lot of other brands and it is hard to know them all) because of their awful record on treatment of workers and even safety (in other words, it is also simple practical
self-interest to not buy food products made by a company that doesn't seem have the will to follow safety regulations).
You're certainly right that nearly all corporations are offending human rights and dignity somehow or other. Since this is 'the way of the world' we can't expect to create large change very quickly or easily. But given some degree of awareness and choice among ordinary people, at least we can have some sort of influence and perhaps keep things from getting worse.