If you wish to line the pockets of tyrants with money, do so with your money, and not with mine.
To bring that which is lost is not only contructive, but grand. It is important for two reasons.
One, it let’s scientists learn and create new techniques in genetic manipulation and engineering in mammals without getting into ethical issues because it is not experimentation humans, but animals instead.
The medical applications in such research is already bearing fruit in geneslicing to treat and cure some hereditary diseases and some types of cancers like leukemia.
Two, it will give a deathblow to the environmental movement because “extinction” will no longer mean permanently lost.
It's hardly constructive, evolution has spoken; the mammoth is no more because it isn't suited for survival. Bringing it back plays dangerous games with the eco-system.