The wildlife officers should not have killed the deer for doing what nature tells it to do. Killing it was stupid.
It is not reported how the man came to be in such close proximity to the deer in the first place, although it is written that the deer premeditated its attack against the man. I suspect the deer was in the guy's garden and he went to shoo it away, putting himself in harm's way. That is not the deer's fault.
People do dumb things around wild animals all of the time and with bad consequences. Even seasoned veterans let their guard down on occasion and get seriously hurt (Sigfried and Roy). There is apparently, for some people, no respect for wildlife any longer. Wild animals bite, kick, gore, claw, stomp, slash, sting, and a host of other bad things. Nothing unusual about that, except some folks just think, in specific situations, that being human is a higher place and forget somehow the rules really do apply to them.
Human reaction in killing a wild animal that has injured a human, and the injuries lead to death, as if the animal had exhibited some premeditated, unthinkable and abhorent behavior, is, if you seriously think about it, wrong. Animals do not premeditate about attacking people. If they did, there would be a lot of dead hunters in the woods every year.