I think there are a couple of things wrong with the argument given. (I'm not going to name a supposed fallacy since this is an inadequate substitute for dealing with the substance of an argument.)
The first is that, as people have pointed out, it is perfectionist. In reality, progress is made piecemeal and so attacking a particular piecemeal change that somebody has made to address some problem is a bad idea. See "The Open Society and Its Enemies" by Karl Popper and "Reflections on the Revolution in France" by Burke.
The second mistake in the argument is that it concedes that the opponent's goal would be good if he carried it out. But often the right way to attack a suggested policy is to attack its goal. I provide these arguments as an illustration. We have selectively bred animals to be tasty. Also animals can't think like people, so giving them rights makes about as much sense as giving your car rights. The only things that animals are useful for are simple tasks that we have programmed them to do. So we have nothing to lose and everything to gain from eating animals. Also, fossil fuels provide cheap, reliable energy that makes it possible for us to have warm houses, clean water, easy transportation and lots of cool stuff like the computer on which I am typing this. Not having cheap, reliable energy is a far larger threat to our future than a change of 1-2 degrees Celsius in average temperature over several decades.