Back in the early days of Internet forums, I posted on one (not MN) as a student, celebrating that I'd been offered a particular grad job.
Someone replied that I was clearly lying because only people with a certain degree could do that job. I most certainly wasn't lying and am still in the same career almost 2 decades later. I will never forget the disdain it was written with by this snooty know-it-all (and how much it hurt as I was only 20 at the time).
I was also accused about lying about my religion because I'd also mentioned Christmas gifts (many of us living in the U.K. do still give Christmas gifts even if not Christian).
Curious to know what else you've been incorrectly accused of lying about online?