Withdrawing fellowship

I completely agree with this.

We have "friends" who are unsaved or not following the Bible and then we have our brothers and sisters in Christ. The fellowship is entirely different with our brothers and sisters and it was confirmed to us on vacation one time. We were away with a group of boats from our club and none of the others are saved. We hung out with them but I commented to DH that I would come home exhausted from being with them. Not exhausted physically but emotionally (and maybe spiritually?). We then met up with a family that we had never met before who were believers and we had dinner together on our boat. The fellowship was so sweet and when I went to bed that night, I told my husband that I felt refreshed in spirit - not exhausted. And these were with people we had never met before! What a stark contrast.

I do believe the OP had a very difficult choice but to be honest with the Spirit within, he could not continue the friendship as it was due to understanding the Scriptures. I'm sure this friend is never far from his heart or his prayers - but the Scriptures do tell us that the friendship is to be severed for the sake of their souls.