Quick Question

I don't think there's like a universal thing you can say, you're your own person you can speak for yourself. Just remember that 'communism never worked' or 'only works in theory' is most often propaganda talk fed to them through majority of society that only highlights the negatives of communism and so to counter it you need to either give them opposite , positive examples and contributions of communism or question them on what they mean by 'it never worked' because that's when you can check if they're just repeating what they've heard for most of their lives or if they're actually interested in the topic.
cheers