I have a strong suspicion about the OP’s beliefs, about the beliefs of the people he wants to argue with, and what he wants to argue about. But I’ll stick to general, abstract principles.
To use myself as an example, I’m about 50 pounds overweight. Therefore, it makes perfect sense that friends and loved ones might feel compelled to tell me, “Listen, I don’t want to hurt your feelings, but at your age, that’s not healthy, and you really need to start exercising and eating less junk.”
Those people mean well, and have my best interests at heart. But there DOES come a point when each of them has to realize, “I’ve said my piece, and I hope he listens, for his own good. But if I push the subject any farther, I may lose his friendship for good. So, I hope I’ve planted a seed in his mind and that he’ll follow my advice later.”
If they CAN’T stop, even after I’ve told them, “All right, you’ve made your point, now drop the subject,” well, I’ll probably just avoid them like the plague forever.
So, the OP has to ask himself, “Which is more important- the relationship I have with this person or being right?”
That’s true no matter WHAT topic you want to argue about. When Jesus sent his Apostles out to preach, he told them, “If people will not welcome you, move on, shaking the dust from your feet.” Note that well. He didn’t say, “Keep screaming the Gospel to them, even if they don’t want to hear it.”
That’s true of weight, religion, politics or anything else. If Grandma keeps telling you, “Listen to Rush Limbaugh with me” after you’ve told her a hundred times that you don’t want to, she’s being a jerk. On the other hand, if you keep trying to convince Grandma that God doesn’t exist, long after she’s told you to keep your blasphemy to yourself, then you’re a jerk.
Get this: It doesn’t MATTER whether Rush Limbaugh is a genius or whether God exists. If you care about keeping a loving relationship with your Grandma, you have to respect each other’s boundaries.