There are 3 species that fit this category for me, because they threaten other species. Two are non-native, European Starling and House Sparrow, and one is native, Cowbird. It has been proven over and over again by science that these three species are playing a large role in endangering any number of our smaller indigenous songbirds.
Is it their fault? No, absolutely not! But that doesn't change the fact that if their numbers are not controlled, they will help (us) push a lot of other species into extinction. They are God's creatures, too, but because of the artificial imbalances that we have created, they are out-competing other species, and if left unchecked, will greatly contribute to the loss of other species. Sticking our heads in the sand won't change that.
This past summer I was in Milwaulkee visiting some friends, and I couldn't help but notice that the only birds in their residential neighborhood were Starlings, House Sparrows, and a few Grackles. Is that what we want?
Cowbirds, being a native species are protected by law, and therefore I can't do anything about. Starlings and House Sparrows, being non-native and not protected, I dispatch with regularity. It's not a matter of hating or despising them, simply keeping their numbers down to give our endangered/threatened species a fighting chance.
While it is true that the decline in many species is almost entirely our fault, invasive species are a serious threat that has to be dealt with along with doing everything else we can to bring back our endangered/threatened species. Things like restoring habitat, controlling invasive plant species, etc. are all more desirable ways to help them, but those are things that the average person doesn't give a hoot about.
Hopefully someday thinning the flocks of undesirables will no longer be necessary, but I doubt it will be in my lifetime. People just don't care enough to do what it takes. They only want "feel-good" solutions to everything that don't involve any sacrifice on their own part. It's the dark side of the human condition, and one of the things that has made us so successful as a species;
unadulterated selfishness.
Sorry for the rant,
Brian