Do you really think that good works justify your salvation in the eyes of others? I know a lot of lost people who do greater works for others than most Christians.
Showing partiality towards the rich or only showing "love" in word and not in deed, can cause MEN to see these "christians" as less than genuine.
God knows who is His. Doesn't need evidence.
Peter denied Jesus before man out of fear, if he did not men would have seen him as a follower of Christ.