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.