It makes it seem like a binomial thing, you are either in my group or in the other. Discussion stops being about the ideas and more adversarial, focused on taking sides.

Also it creates a group identity which in my opinion makes it harder for people to change their minds based on discussion or new info.

If my aunt tells me vaccines are bad I might trust her. But if there is whole group of 'anti-vaxxer' people who make me feel good about myself then I suppose I am now an anti-vaxxer and that becomes an identity more so than an opinion which would be more fluid and mutable.

Statistically, you will have children in future, if you’re under 30 right now.