I don't believe that euthanizing 8 dangerous, problem crocs is going to endanger the environment.
As you point out at other times, the "normal" croc in the wild is not really a threat. I don't advocate wholesale slaughter, but putting down the problem ones seems not only sensible, but mandatory for public safety.
The crazy part of this whole "relocation" thing is that the pubic can't tell a "good" croc from a "bad" croc. So now that we know you are dumping killer crocs around, and that additionally they will re-appear at the scene of former crimes --- we've got a situation where virtually every single croc people see may be suspected of being one of the killer-8.
My guess is that a fair amount of the general croc population will meet their demise as a result ------