If I understand you correctly, you are saying I was right to speak up and get my relatives mad at me.
If I keep it up, none of them are going to want anything to do with me.
1. You didn't get your relatives mad at you! They allowed themselves to get mad. And, it certainly wasn't your intention to provoke them, correct? Assuming this was true, there was no fault committed on your part.
2. I am NOT advocating that wisdom and prudence be abandoned. What I am saying is that there are times when one must speak up for the sake of honoring God's name and demonstrating your deep commitment to Him which is the fruit of your union with Christ and the influence of the indwelling Spirit. Yes, there are times when it is most wise to keep silent. It is always a judgment call when it comes to these types of things.
3. Would it be so terrible if your godless relatives didn't want anything to do with you? Would the world suddenly come to an end? May I suggest that your relatives future, unless God grants them mercy through His ordained MEANS, is one of a fiery hell and eternal torment. The things that you described only served to add burning coals to their heads.
4. The basis for the wisdom you seek is found in Christ's own words:
Matthew 10:32-41 (ASV) "Every one therefore who shall confess me before men, him will I also confess before my Father who is in heaven. But whosoever shall deny me before men, him will I also deny before my Father who is in heaven. Think not that I came to send peace on the earth: I came not to send peace, but a sword. For I came to set a man at variance against his father, and the daughter against her mother, and the daughter in law against her mother in law: and a man's foes [shall be] they of his own household. He that loveth father or mother more than me is not worthy of me; and he that loveth son or daughter more than me is not worthy of me. And he that doth not take his cross and follow after me, is not worthy of me. He that findeth his life shall lose it; and he that loseth his life for my sake shall find it. He that receiveth you receiveth me, and he that receiveth me receiveth him that sent me. He that receiveth a prophet in the name of a prophet shall receive a prophet's reward: and he that receiveth a righteous man in the name of a righteous man shall receive a righteous man's reward."
Perhaps it is more prudent to have God's favor than that of your relatives? What could they possibly do to make your life better compared to what God has done for you in Christ and the glory that awaits you IF that is your first love?