It's super annoying when someone talks to you like you're five years old. But it's even more annoying when they're talking to you like you're five years old about a subject you know way more about than they do!
Most of the time it's best to be gracious and humor someone -- even if they've made the erroneous assumption that you're an idiot. But when they combine condescension with just being an overall jerk... it can be hard to hold off teaching them a little lesson.
The following experts in various fields recently took to the internet to share stories of know-nothings who tried to lecture them and ended up getting a lesson of their own instead.