Burger King and KFC have launched their first plant-based burgers – but not all vegans are on board. As Burger King’s soy-based Rebel Whopper is cooked on the same grill as meat, many non-meat-eaters are refusing to eat it, while KFC has admitted accidentally selling chicken to vegetarians who had ordered its new vegan burger.

Plant-based options at meaty fast-food chains create moral dilemmas for vegans – a result of longstanding concerns over their treatment of animals – but Toni Vernelli, the head of communications at the nonprofit organisation Veganuary, says it’s important that vegans show demand for these products.

“Fast-food restaurants don’t have a particular vested interest in serving up dead animals,” she says. “They just want to serve products they can make a profit on. So, if we can help them make a profit on products that don’t involve dead animals that can only be a good thing.”

However, José Cil, the CEO of Burger King’s parent company, has said that, when the chain launched the plant-based Impossible Whopper in the US, meat-eaters continued to buy beefburgers at the same rate. “We’re not seeing guests swap the original Whopper for the Impossible Whopper. We’re seeing that it’s attracting new guests,” he told investors.

The perception that vegan alternatives are more about profits than ethics puts some vegan consumers off. “It’s obvious to me that these options are just to bring in new customers,” says Nancy Nussbaum, an animal rights activist. “They’re not going to stop animals being killed. Activists are exposing the suffering and slaughter these chains inflict on animals. The bosses are terrified, so they’re trying to buy us off with these products and pretending they’re our friends.”

Karin Ridgers, the founder of the online channel Veggie Vision, has seen the dilemma play out in her own family. “I’ve been a vegan for 25 years and I’m not going to set foot inside KFC or McDonald’s,” she said. “But my son is 13 and he’s vegan. When he heard about the Greggs vegan sausage rolls, he said: ‘Mum, I can now go into Greggs with my friends. I’m not the odd one out any more.’”

Vernelli believes fast-food options are important for the image of veganism. “We’re constantly told veganism is expensive and a middle-class privilege, so this helps counter the argument that it’s elitist,” she says.

As veganism enters the mainstream, these kind of debates are inevitable. Vegans will have to decide where their boundaries rest.