Political brainwashing, that's why. This is exactly how it works. You take an issue (social, cultural, scientific, religious - does not matter), use it as a division line between "us" and "them", pick a side, them bombard "us" with messages that dehumanize "them" to the point where there is no possibility of rational conversation between the two sides.

Bam. Now you have political control over a group of people, and that control can be exercised outside of the context of the original problem.

It is very unfortunate that ecology was chosen as one of the issues to politicize, because it already was one of the most complex fields of research there is, not to mention that issues in that field have potential to affect most of the people on the planet.

My advice? De-escalate the rhetoric wherever you can. That's the only way forward in the long run, for everybody.