What a frickin' stupid straw-man argument.
Nobody is claiming "Theft never occurs". Nobody.
But even if stores lose some of their stock due to shoplifting, etc., the vast majority of people in those stores are there to make legal purchases. The fact that the CVS pharmacy that Rittenhouse was watching (while making his "shooting people" comments) was still open indicates that most people at that store were not stealing, but instead were actually spending their money to receive their product.
Unless Rittenhouse was omniscient, or had some other way to determine someone was stealing, he could not tell if people leaving that store had made legal purchases or not, since most people in stores do not steal.