It’s so much easier for most people, mentally, to trash someone that they disagree with, using the worst possible insults, than to allow the possibility that they might have been in the wrong.
This is why an instruction as simple and non-controversial as “be respectful” encounters such fierce resistance.
When you encounter this attitude, as we all eventually do if we spend any time on ImgFlip or elsewhere on the internet, just remember that it is the sign of an insecure mind and nothing more.