There are multiple definitions of the word "selling". The poster is referring to what salespeople do, not what a grocery store does.
There is no way to avoid selling in life. Otherwise, at the least, you will be constantly overlooked. There should be no shame in it. The shame is only when sales replaces instead of presents the value proposition you are offering.
Engaging with certain salespeople is an altogether different proposition. In order to buy a car, you are forced to interact with multiple odious people who have ripping you off as their sole objective. Thats what I think of when I think of a “salesperson”. See also mattress stores, wireless carrier “retention” departments, HVAC installers, etc.
But also buy, within reason, stuff that's on sale, looks good, etc. Otherwise just order on-line.