Yes, 'derp' is a modern jargon expression for saying 'stupid!' or 'doh, that's obvious'. When referring to groups of people who exhibit idiotic behavior, 'derps' is now a common insult name. Use of the word derp is very common in online gaming, Reddit commentaries, and Facebook posts. Whether you see it spelled as 'derp' or 'durp', the meaning is the same: someone is getting insulted.

“Derp this derping derp!” ~An actual quote from a forum user.
Yes, this is quite the interesting phrase, and it could be potentially abused in so many different ways. The internet is becoming increasingly hard to control. For the better I guess.
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I never heard of ‘derp’ before, I wonder if the word has made it into my part of the world yet. I’d be interested to know the roots of the term. It sounds rather like one of Homer Simpson’s nonsensical bleatings – ‘Doh!’