All sounds very plausible. However..
There is a curve chart somewhere in this. As you shop with smaller large companies, their ethical stance gets better. Thus proving you don't get to the top by being nice.
However, you then start curving the other way as you reach the companies who claim they can't afford to look after their staff and suppliers as well as larger companies.
After that come the small companies who can't compete with larger companies which limits the spending power people have with them.
So, more and more, this stance becomes a feasible tool of those with more spare cash than others. As I noted above though, you don't get to the top by being nice.
I note hat despite such mass action attempts, Nestle are still turning a decent crust for their shareholders.