Sometimes you have to cut your losses and leave a conversation. If it’s some rando on the internet, just walk away and try not to care what they think.
With people you know and respect, you’re gonna have to hunker down for the long haul. Remember, if you come off like a jerk, they’re going to be less likely to accept your argument. Be respectful of their position but ask probing questions. Let them see for themselves that they’re wrong.