If humans are a cancer on the earth...

It would be specifically diagnosed as leukemia.

Leukemia is the result of hate, rage, and resentment. These emotions interfere with the signal your body sends to each cell. A cancer cell has lost contact with the signal, goes rogue, and multiplies out of control. Cancer cells will then also recruit healthy cells. Leukemia is a blood cancer in which white blood cells (the helper cells) multiply out of control and attack the body instead of the diseases they are meant to attack.

Now look at every form of SJW. They are helper cells that are out of control.
They DO have a beneficial purpose. They may even be aware this drive from within. They are consumed by the hate, rage, and anger of the world and don't know what to do. They become filled with these emotions. They don't detect the signal from God or the Earth. They fall for any kind of group think because they don't have the personal connection or the confidence that comes with it. They are easily recruited into ideas that allow them to think they are helping while they are actually attacking (the body) Earth and other humans (cells).
The raged helper (out of control white blood cell) is not a good combination. The rage motivates them and this is why they are so forceful with their ideas when attempting to recruit others.

This has been a result of many things but what is more important is that we are now healing.