The virtue involved in helping those one loves is not “selflessness” or “sacrifice,” but integrity. Integrity is loyalty to one’s convictions and values; it is the policy of acting in accordance with one’s values, of expressing, upholding and translating them into practical reality. “The Ethics of Emergencies,” The Virtue of Selfishness, 46
This can only be true if one values "love" as an "ultimate value". Relationship with those that have different values must be mutual compromise, or dissolving one's association to such a relationship. If the principle or value is too important to compromise without loosing "self-respect", then, compromise is asking the impossible. Self-respect is the foundation of integrity.
No one should be required to "help" in those areas they do not believe in. And no one that loves another would ask them to "help" in the areas they do not believe in.