Hehe, there you go again with that slippery slope fallacy.
Perhaps a fallacious argument, but if this attempt is actually both viable and successful, it will be tried again. As you stated earlier, bringing an extinct organism back into existence for scientific research is a good thing. So once we've learnt all we can from mammoths, it is a logical assumption some other alternate life form will be cloned to further extend scientific knowledge. For example, if you ever want to clone plants for such medicinal purposes, you'll have to test your scientific method on
something other than mammoths. Apart from the obvious fact plants are not mammoths, I would suggest that making the 'jump' between merely cloning one species of animal to a variety of plants is improbable, if not impossible.
But what do I actually think of cloning? Meh. If they want to bring back a mammoth from extinction for testing, I wish them luck discovering something useful to broader scientific knowledge. If they start bringing recently eradicated species back from the dead, meh, if the reintroduction of the species is viable then thumbs up to them.
If they want to clone 500 mammoths to overrun the streets of Tokyo, then lol. There is a reason these animals don't walk the earth today - the climate is not suitable for their survival. Above that, it is my understanding that unless we have mass amounts of DNA, they couldn't get enough genetic variation to encourage successful offspring equipped for survival anyway. If they actually can reproduce without having two heads or five legs, their inability to adapt to climate change in addition to the presently unsuitable climate would knock them yet again.
As for the possibility of human cloning - good luck with that. At this stage I'll jump on the slippery slope fallacy train hehe. Whilst I can imagine us having the ability to replace faulty organs in a heart beat, cloning brains or bodies would more than likely cause so much public outrage it wouldn't be permitted to occur. And that's assuming such possibilities became realities during any of our respective lifetimes, or even at all, which also is not a guarantee.