2. Used as a reply to an insult when you have nothing else to say to defend yourself
3. Used to change the subject when someone insults you and to avoid embarrassment.
4. also can be used to lower the intensity of an argument after someone insults you, simply because there is no good response to "duh guys"
must be said with an embarrassed tone and look on your face in order for these meanings to take effect
used when talking to friends on facebook or in person after being insulted and feeling embarrassed in front of a group of people
(a friend) "that is the stupidest joke i have ever heard in my entire life, are u such an idiot"
(you) "Duh Guys"