People like this are called Luddites. It's an old, but rarely studied mental illness. You can look it up.
Such an EMP attack might put a stop many types of pollution. It would put a stop Genetically Modified Foods. And it would seize up the "Global Warming" process ... or it might not.
It would certainly put a stop to our ability to accurately study Global Warming.
It would also shut down Hospitals, Retirement Homes, Rehab Centers, and Medical Research Facilities. Many millions of people would die, as they would no longer be able to receive the various kinds of care they currently receive.
Luddites would be happy about this because they believe our Earth needs less people anyway. They like the idea of culling the herd.
Few Luddites believe themselves to be among the herd which needs to be culled. Luddites believe they are a noble elite. And they believe, if the world were returned to it's "Natural State", it would enter a Golden Age, wherein the remaining humans would recognize the brilliance and pure personal power of the noble elites who had envisioned and carried out the Luddite Dream of destroying civilization as we know it.
This Noble Elite of Luddites would then reign as Kings and Queens of Benevolence and Graciousness, tilling the Green Earth, and sharing all things as human beings were meant to do. There would be no more tears, no more pain. There would be only a kind, Communal existence, similar to the more fevered episodes of My Little Pony, or the Care Bears, or the Teletubbies, but without the TV's on their Chests.
Yes, the Luddite Dream is a thing of beauty. It is truly a unique product of the Human Imagination. It is alive in many of us, and animates quite a bit of our political discourse.
But, there are other ideas alive in the imagination of Humans. For instance, some people dream of giving the blind eyes to see, and the deaf ears to hear.
And, some people are making those ideas come true, with the aid of very Advanced Technology: