Sometimes people believe what they do not because it's true, but because they want to believe it.
It is common for people to make decisions based on how they feel and then later try and justify their choices. This is especially true of religion where they fill in the blanks with [deity].
This is what a lot of anti-vegans do, too; labelling, stereotyping, and mocking vegans and veganism. The same is true for other pejorative labeling (SJW, RWNJ, feminazi, pedo, nigger, etc). Things tend to go by how you treat people.
People can change their mind on religion, too. But what I find is the problem with religion is that they don't want to. Religious faith is belief in things that are not evidently true. It demands denial of evidence and reality (to avoid eternal hell, etc). (Edit: religion is often inculcated from birth.)
For people trapped with unjustified or unfalsifiable beliefs, telling them they're stupid or laughing at them, makes them double down. That approach might work in public debate but it's not going to work well for interpersonal relationships.
People change their mind and they will when they are ready
I find reasonableness to be the most important factor.
