This is a very low-quality comment.

First, the difference between being mistaken and lying is intent. The site guidelines call for being charitable. So unless you can prove intent, don't call out someone for lying.

Second: Just saying someone is wrong/mistaken/lying turns into a five-year-old's argument: "Am not!" "Are too!" That's not a useful conversation, nor even an interesting one. Instead, supply some evidence that the rest of us can look at and judge whether you're right. (Actual evidence might even convince the person you were replying to - some of us here do actually listen to facts from time to time.)