The last sentence serves a purpose though. It urges the commenter to reflect on their own industriousness or lack thereof perhaps causing them to modify the standard by which they judge others.

Insults tend to make the recipient defensive. If you want the commenter to rethink things, there's not much benefit in insults.

It's hardly an insult though. You have to have at least the slightest thickness of skin to survive on the internet or to even just to practice self reflection.

There are two, not exclusive ideas here. First, when you are reading comments, you need a tough skin. I agree. Second, when writing comments, you can try not to be needlessly antagonistic. I hope you can agree with that.