Well where I live kangaroos are seen as pests for the most part because they eat farmers crops and they also cause a lot of motor vehicle accidents. And hunting with dogs is quite common. So as a kid at the time I didnt feel as though I was participating in anything too bad. All of the parents of these kids knew exactly why they owned the dogs and what they were doing with them. I had a friend thats father bred staghounds. For hunting.
But yeah - kangaroos are culled around here - they are pests and their numbers get out of hand. The legal way to do it a farmer calls in a culler and the culler has tags issued to him by the state and can only kill as many kangaroos as he has tags. You need a license for it. The kangaroo culler sells the meat or skins. But mostly a farmer will just shoot kangaroos themselves - or allow shooters onto their property to kill roos.
Sometimes we did 'rooing' on a farm and we would all ride motorbikes and a few would have four wheelers with the dogs on the back. Its a bit different to doing it on foot because there is no stealth - its about chance and speed. We used to ride dirtbikes out at The Common but never for rooing - it wasnt a large enough area. But on a large farm you can do it with bikes. The best way is on foot though like I described above.
So since kangaroos are pests what we were doing was wildlife management.