Friends with Non–Protestant Reformed People

Is it spiritually dangerous for a young believer to have friends from other denominations/faiths? How should we interact with family members we value who hold different faiths, for example Roman Catholics?  Spiritual danger really amounts to this: Is it a temptation to sin? Is friendship with a non–Protestant Reformed person an enticement to sin? Undoubtedly, friendships for young believers are extremely important. A friend should be what Jonathan was to David: a confidant (someone whom David...