Students held a "Big Kiss-In" at a branch of Sainsbury's in Brighton after a lesbian couple were asked to leave the store for kissing.
Dozens of people, including one woman in a wedding dress, descended on the store on New England Street on Wednesday as customers shopped around them.
After the event, the student union at Sussex University tweeted: "Thanks to everyone who took part in the #bigkissin. Great to see people in Brighton and beyond showing we like kissing and hate homophobia."
Annabelle Paige, a Sussex University student, was shopping at the store on Saturday when a customer complained about she and her partner kissing.
They were subsequently asked to leave the store by a security guard.
Ms Paige told The Times that she had only given her partner a light kiss.
She said: "I'm so shocked and upset about it. I get that if another customer is uncomfortable that's a bad thing ... but the problem is the other customer was in the wrong and essentially being homophobic."
Sainsbury's has apologised, saying in a statement that the couple "were not behaving inappropriately and we are very sorry that they were treated in this way".
A spokeswoman for the supermarket said of the protest: "We understand the point that people were making and we were happy to welcome the Big Kiss-In to our store.
"We're pleased everyone had fun and we were happy for the chance to remind everyone just how important being an inclusive business and employer is to us."