1. The absurd proposition that it's unjust that you will find a better deal if you spend more time looking for one. Of course you will.
2. The claim that e-commerce is a regressive tax on the poor because purchases are bigger percentage of the poor's income. You can say the same thing about any purchase. A burger is a bigger percentage of a poor person's income than a rich person's income.
Paribus is providing a great service, but this is a marketing/PR article pretending to be serious economic commentary and analysis. It's just hopping on the bandwagon of a narrative that's politically en vogue (that the world is stacked against the poor).