Yes, when someone says something "doesn't exist", that doesn't automatically mean "in all conceivably possible ways". Different people have different perspectives and context in their mind when they say things like that, so we have to be careful in how we interpret their words as they don't always mean them as literally as others might assume... language is hard.

Sometimes it helps to ask clarifying questions like "what do you mean they don't exist?" instead of assuming their perspective is the same as yours, and then sending a reply that doesn't make sense... that's a very easy way to start an argument.