You’ve been dating this man for 6 years and you’ve known this boy since he was 11. He’s now 17 and is still being rude to you. In your last letter, you said your boyfriend believes that no matter how his son treats you, you need to love him, respect him, and make him feel welcome. He doesn’t think his son should have to reciprocate. I disagree.
Please remind your boyfriend that I did not say that the boy should love you, or even like you. I am, however, strongly of the opinion that it is not asking too much for a young man to have good manners, nor is it asking too much of his father to insist on it.
Making polite conversation with the partner of someone you love, regardless of your own feeling about the person, is part of being a mature adult. If the boy comes home with a girlfriend you and his dad aren’t crazy about, he’ll want you both to treat her well (as you should). He should be expected to do the same for his dad and for you.
At this point, I think your problem is with your boyfriend as well as with the young man. It’s your boyfriend’s job as a father to teach his son good manners. After 6 years together, it is only reasonable to expect that he teach his son how to treat you properly. If he can’t do that, he should at the very least be willing to give you an honest explanation and an apology. Only you can be the judge of whether his reasons are enough to compensate for living with the situation as it is.
I wish you well.