I've been on both ends of this, as a DJ and as a FOH sound technician. I've had problems with stupid DJ's that overdrive their signal before it even gets to my mixer so it obviously gets distorted, and they look at me like it's my fault. And I've also been a DJ that needs to turn the music up more so I can monitor it.
The best way to deal with this is to do a proper sound check before you start. Put your end as loud as it will go and tell the technician to adjust appropriately, and keep in mind, what sounds loud in an empty room can sound like a whisper on a crowded dancefloor. So turn it up LOUD. Then simply tell the technician not to touch it or you'll kick his ass, and then adjust the sound yourself.
I know it's even more work to have to DJ and manage the house sound, but personally I like to be in control, and if something screws up, everybody's going to be looking at me, I at least want it to be my fault, and not some technician hiding in a back room making me look like a jackass.