Accused of shoplifting for collecting groceries in a reusable bag

I don't like using plastic baskets provided by the store because they're really dirty. I've seen kids standing in them with their shoes, and our neighborhood is full of homeless people who spit, urinate and shit on the sidewalks.

Anyway, I was accused by a homeless person in the store (not an employee) of stealing and he kept following me around and yelling at me. I paid for my groceries as usual and walked out without any problems. But it made me wonder whether I should stop collecting groceries in a reusable bag.