The IT job market is a two sided lemon market, people may lie on their CV but companies can be very abusive as well. If you don't do what OP suggests, people will not respect you. I've had five developers join my interview call to see if I can implement a palindrome checker. This is proof that non of them bothered to read my CV and check out my github projects. This is not respectful, and you have to stand your ground against such nonsens. Let them now this is not what you expect from people working for you and and that you expect better from them in the future. If they don't like that you won't have lost anything.
Was it the task itself you feel was disrespectful or the way they ran it? Anyone can put up fake/inflated CV so it's not really proof they didn't bother to read it, GitHub can be easier or harder to fake/inflate depending on the projects. Doing something like a quick palindrome checker to show "Hey, yep - I'm real not some random inflated applicant you probably got 10 applications of alongside mine" seems more than reasonable/respectful (by both sides). I can also easily see how 5 people can hop on and completely run that task in the wrong way and come off as being know it all douchebags or the like but that'd be a different independent issue really.
