Demean the work, don't say anything about him but minimize the value of what he is doing. Commiserate how bad it is that he has to waste a day doing something with so little value. Be on their "side" but make it clear you "understand" what they are doing isn't valuable.

All of these comments should be said in group setting to try and get the crowd to pickup similar views. Just make sure no one thinks of what they are doing in a positive light.