From my experience owning a 2003 F650GS for 3 years, I agree that ABS sucks offroad. Often when braking on loose ground the wheels will slip just a bit activating the ABS and lengthing your stop substantially. When braking offroad, you want your tires to bite into the ground and build a wall of resistense in front of them. With ABS the wheel cannot lock and therefore cannot do this.
Most bikes intended to take offroad that have ABS also have a switch to turn it off. My BMW did anyway...
2002 Tacoma double cab
3RZ/5speed (W59)/locking hubs
Aussie locked front
Bold on TG sliders