Selling ANYTHING is demeaning? So you believe the only non-demeaning way to live would be to live entirely self-sufficiently, making and growing everything yourself?
Grocery stores are experts at sales tactics throughout the store. All that fruit does not look so beautiful in the field, and virtually every store is trying to develop their 'ethos' to capture the customers with enough money to be able to care about that.
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.
There is a trivial defeat for nearly all grocery store sales tactics: make a shopping list.
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.