It's an ill wind that blows nobody any good

With the recent story of former NASA employees telling NASA to stay away from the climate change argument, it once again causes me no end of confusion about the vast majority of climate change deniers. And despite their claims of being "skeptics", they are not; they are full-blown denialists, unwilling to look at the hard data or accept the conclusions of the hundreds of scientists who's jobs are to figure this stuff out.

The main point that I do not understand is why they are fighting so hard against the evidence that man is changing the Earth's climate. As a simplification, I'm going to look at the four major possibilities we have in regards to climate change:

1. Climate change is happening, but we don't do anything about it
2. Climate change is happening, and we fix the problem
3. Climate change isn't happening, and we don't do anything about it
4. Climate change isn't happening, but we change things like it was happening

Climate change is real, we do nothing
The science is real and our pollution and actions are changing the environment of the planet. Temperatures continue to rise, glaciers keep melting, severe weather events (hurricanes, tornadoes, droughts, etc.) continues and maybe even get worse. Within some number of generations, the environment will be damaged beyond repair and global resources will become very limited, wars will start, millions will die, and the human race as a whole will be in significant danger.

Climate change is real, we fix it
The environment improves, glaciers do not melt, severe weather gets a little less severe and frequent. The planet is still able to provide enough resources for the future generations (until such time as resource requirements exceed the planet's ability to generate).

Climate change is not real, we do nothing
Nothing significant happens. The environment stays about the same, or at least gets no worse than the current path. Global resources will continue to provide for future generations (until such time as resource requirements exceed the planet's ability to generate).

Climate change is not real, we change things as if it was
The environment improves, global resources last longer (renewable energy by definition will last longer than fossil fuels). The planet is still able to provide enough resources for the future generations (until such time as resource requirements exceed the planet's ability to generate).

Yes, I realize this is a very simplistic view of a complex issue, and ignores things like costs and technological improvements, but at the base level, it seems to boil down to this:

If we act like we are causing global climate change and work on fixing what's causing it, at worst, we are spending a lot of money to make the planet better for future generations; at best, we are saving future generations. If we do nothing, at best we are making things no better or worse for future generations; at worst, we could be dooming future generations and perhaps our entire planet.

Seems like we have really have nothing to lose and everything to gain by just assuming the scientists and data are correct. If they end up being wrong, well, at least we'll have a nicer planet to live on.