Your acquaintances are doing the wrong thing. No member of the public should take it upon themselves to cull any species, unless advised/permitted to by an official.
As for the culling of 'pest' species, that is a really difficult thing to consider. I was raised to care about the environment first and foremost, but my love for individual animals makes the thought of culling really difficult. I am not sure what damage noisy minors do, I suppose they breed more than other species and may be taking and defending more than their share of natural bushland... That is not good. On the other hand I have personally rescued and helped raise a noisy minor chick that I found on the road one day. It was a tiny little sweet creature, and upon taking it outside one day found that other mothers in the area responded to it's chirps and came to feed it. Before long it had grown up and flew away with it's new adopted family. That was truly wonderful.
Perhaps I did more harm than good. Perhaps I should have let it die. I don't know. I feel like I did the right thing. I don't think I would have been strong enough to let it die anyway.
The whole pest/culling/environment discussion is really difficult. I guess at the end of the day I have to support it when truly necessary and when ALL other options have been exhausted.
It seems to come down to the horrible choice of who gets to live and who gets to die. Feral animals or native animals? They both have the same capabilities of suffering but you have to make the tough choice of which is better in the long run.