Personally I have casual sex, happily and enthusiastically, but I never have meaningless sex. I think that sex that doesn't lead to a romantic relationship is just fine, but I'm deeply opposed to having sex that anyone thinks is meaningless, because meaningless sex seems to me, ungrateful. I think that if you think having sex is meaningless then you're not properly appreciating sex (like we don't properly appreciate so many things) I think that when we have sex we need to for a moment think "This feels great, I'm really grateful to be having this experience right now" the same way when we eat a candy bar we should think "this tastes great, I'm really grateful to be enjoying this candy bar." less