Capitalism will work better if sellers are forbidden to discriminate among buyers. It would be even better if buyers were forbidden to distinguish among sellers
First off, you are confusing capitalism with a free market. They explain different aspects of the economy.
That said, you then created a straw-man argument by providing what you consider a perfect free market and then shooing down why it is not economically realistic. I made no claim that a perfect free market is an achievable or even desirable situation. I merely provided a quid-pro-quo pithy aphorism to highlight different techniques each side of any economic exchange uses. If buyers want to take advantage of quick and easy access to price comparisons, they are hypocritical to also complain when sellers take advantage of similarly available information to perform price discrimination.