How long does a fish have to be in our waters before it becomes native???
They have been there for hundreds of years, they haven't done near the damage to our fisheries and "native species" the man has done. By the way if you went back in time to before when carp where released into the wild, you may be surprised at what is really native to a body of water and what is not.
If you want to just hate the Common Carp because they are a Common Carp that is fine but don't hate them because we stocked them there hundreds of years ago. Also don't hate them because they share the same last name as a couple of new comers to the water ways that have people freaked out, that is like you hating my Great Great Great GrandUncle twice removed because I ran over your favorite mailbox.
I wonder if in 300 years people will be complaining about the state stocked trout, steelhead, stripers and the list goes on and on that have been introduced to bodies of water that never had these species before?