For some, it's about the principle/value alignment. Similar to how you'll likely be happier (or at least have fewer conflicts) with someone who shares your diet

For some, it's about the principle/value alignment. Similar to how you'll likely be happier (or at least have fewer conflicts) with someone who shares your dietary preferences or religion. Sometimes it's no big deal, and I'd recommend your advice. But if it is a big deal for someone, then just be up front about it and why you will/won't do it.