If someone posts a demonstrable lie or falsehood, or continues to post a demonstrable lie

[cleanhippie]

or falsehood, is it ok to label that person as a liar?

If not, why is it ok to post a blatant lie or falsehood in the first place, or to keep repeating the lie or falsehood?

[EarlG]

1. We consider it a personal attack to call a person a liar

If you see someone posting a lie then we prefer you to go after the post itself and refute it with facts. This is because our rules are based around the idea that it's okay to attack ideas but not people.