Asceplias, what this young lady has is a root of bitterness. A root of bitterness comes from being with others who have it, listening to their bitterness and permitting it to come into your own heart and take up residence. Racism is the fruit of a root of bitterness.
When you note someone with a root of bitterness? You need to separate company from them and have nothing to do with them. It does not matter who they are. You have to walk away. If they have a teachable spirit you could tell them what you see and admonish them to repent but if not I would just walk away. Continue to pray for them but don't have anything to do with them. Here is the scripture about it.
It is written:
Looking diligently lest any man fail of the grace of God; lest any root of bitterness springing up trouble you, and thereby many be defiled.
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As you can see a root of bitterness defiles others. How? By listening to their bitterness and making it your own. It will defile you and eventually you'll be walking in unbelief. Which will rob you of eternal life. Is it worth it? No.
I disagree on 2 of your points. Bitterness is a product of racism not the other way around. Some bitter people are worth helping.
Yes, by prayer and giving them the Word of God. You cannot talk a person out of bitterness. It is a spiritual condition. You are stating that Bitterness is a product of racism. You may as well say Fruit. There are many fruits of racism - envy, murder, strife, hatred, jealousy, wrath....and as you see - none of it is good. Today in America there is racism found in all races of people. There are Chinese people who are racists, Russians who are racists, their mindset is one of superiority - that they are the super race - it is no different from the white man who thought he was superior to the black man because of his skin color.
Do you know that if a Christian judges another person by their skin color - is a racist against African American people - that they will go to hell? It's true. You cannot hate a black person because they are black and go to heaven. It's not happening. Did you know that there is no such thing as a black person who is a Christian - going to heaven with hatred in their hearts for white people? They cannot go to heaven either. So racism is caused by a Root of Bitterness that will literally bring you into a state of unbelief ( even unbelief that you could lose your salvation over it!) and cause you to lose your eternal life - in heaven- leaving only one place to go. Hell.
How terrible is that? That is why I would advise this young man to RUN not walk away from this relationship.
As Christians we need to walk in forgiveness. If the waitress was in any way a racist? It's her problem and the right answer is to pray for her and ask the LORD to deliver her of it. Are there white waitresses that are racists? Absolutely. Are their black waitresses that are racists? Absolutely. God isn't looking at the color of one's skin. He is looking at the what is inside the heart. That is where we will be judged.
You should guard your heart with all diligence because out of it flow the issues of life. I have to guard my own heart. You'd be surprised how easily the enemy can try to come in with some small suggestion. It is the little foxes that destroy the vine. You have to be vigilant. Cutting off the relationship is being vigilant.