It their purposely acting like a total idiot or they do something really, really stupid then yes. Thought if they tried something or did something thing wrong that made them look like a idiot, the no, or course not. That's would be rude and not very nice if I did.
Technically, in people's mindset, an idiot is anyone who is by anything more than a small amount less smart than you. There's no chance I'm not an idiot to some people. And I can say for sure that a lot of people seem dumb to me. But knowing that to many I'm an idiot leads me to conclude that mocking those who are idiots to me (while not really a believer in karma) seems like a mean thing to do.
Idiots = subjective.
Except Joey Essex. I probably laugh at him a fair bit.
Something I've learned (the hard way) is that there will always be someone who knows more than you do. So, it logically follows that you will always be an idiot compared to someone. So, if you laugh at those who are idiots compared to you, you are proclaiming that you deserve to be laughed at as well.