Offering free shipping is not a problem. The problem is that mandating your suppliers subsidize free shipping and don't sell for cheaper prices elsewhere is blatantly anticompetitive, and has the effect of raising consumer prices on non-Amazon markets.
I agree with that, and I think buy box suppression should be stopped. I’m just responding to the opening paragraphs of the link (and some near the end) where the author appears to be arguing against the very conception of free shipping as if it’s something that can only be offered in distorted and monopolistic markets.
