Your uncle apparently wants to do what is right, and I hope you will respect him for the good things he does (and the bad things he avoids doing). The Bible tells us to "Avoid every kind of evil" (1 Thessalonians 5:22).
But your uncle may have overlooked one of the Bible's most important truths: When we come to Christ, He wants to become the ruler of every area of our lives -- including our money. From what you say, over the years your uncle has been very careful with his money, and this may be one reason for his success. Hard work and thrift aren't necessarily wrong; the Bible says that ants are "extremely wise" because "they store up their food in the summer" (Proverbs 30:24, 25).
But thrift can easily turn into greed -- and greed makes us stingy and grasping, and also causes us to be selfish and insensitive to the needs of others. Jesus said, "Watch out! Be on your guard against all kinds of greed; a man's life does not consist in the abundance of his possessions" (Luke 12:15).
Pray for your uncle, that he will turn every area of his life over to Christ -- including his money. And if God opens the door for you to say something to him, express your concern about this. Most of all, make sure of your own relationship with Christ. Have you given your life to Him?