Eh, in my mind the big mitigating factor is that it's not a mistake that's particularly hard to undo if there are indeed negative environmental consequences. P

Eh, in my mind the big mitigating factor is that it's not a mistake that's particularly hard to undo if there are indeed negative environmental consequences. People won't be thrilled about a mass Hippo cull, but... it's not hard to find and kill 1,000 pound animals, in the way it is with Pythons. Our ancestors were great at it. We did a great job with the Buffalo, and Sloths, etc etc. We're doing a great job of wiping out the megafauna that does remain, all over the world. So I don't personally see a big risk to letting the population grow to a few thousand and seeing what happens. If it goes poorly, we're very well equipped to re-extinct them.