Unless your friends have experience building a business, I'd take their opinions of building a business with a grain of salt.

They might mean well, but it doesn't seem like they don't know what they are talking about. They might even want to believe it's impossible, so that they don't need to admit they aren't as ambitious and couragous as you.

Probably best to avoid this topic. Ask them to respectfully stop telling you it's a bad idea and focus on topics that you can have a productive conversation around. If that proves impossible, reconsider what the friendship is providing you.

I'd also consider finding additional friends that do share that entrepreurial mindset. It's a long road to go on all by yourself. Being on WIP hopefully helps, but there's nothing like having IRL chats with like-minded people.