No they don't stay localised - and when they move on, and it causes issues, then culling is reasonable. Or you cull populations at the point where population pressure is likely to push towards unmanageable expansion.
There's always going to be management involved. And with management, cost.
I'd agree, but I can't help thinking that's a bit of a straw man. I'm not sure anyone believes that such projects are without potential consequence. There's just a big difference in how much weight some people put on the action,