Animal rights campaigners crowded the entrance to Chelmsford city centre's Ladbrokes.
Staff at the betting shop called police, but they told Ladbrokes "everyone has the right to a peaceful protest".
The three people from Essex Animal Defenders, who usually protest at circuses and fur shops, were handing-out leaflets protesting against horse racing in the High Street from about 11.30am to 2pm.
"We have those who have the hump with us and tell us to get a job," said campaigner Marcia Hagon, from Romford.
"But that's the gamblers being defensive and shows we're probably teaching them something. But people believe what they want to and anything that goes against their beliefs they just don't want to hear about."
Marcia added: "One girl went away and came back and said 'no, I am not going to bet any more'."
They claim another woman said "all the more to eat" when she was told two horses had died at the Aintree meeting before the Grand National started.
