Why do atheists on social media seem so rude?

Each time they see a post about X religion, they always feel the need to add their own unsolicited opinion (even in cases when it wasn't asked). Also, they are unwilling to engage in any kind of constructive/civilized discussion, but namecall others. I don't understand why can't people be more respectful to each other, whether they believe in the existence of a God, or not. I don't know if anyone else has had a similar experience to me.

Why do atheists on social media seem so rude?
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