That struck me, too, so I reread, and the point is that disagreement was produced by mixing students from Latin America with a class in continental Europe.

I noticed that too, but I think it doesn't really undermine my point that he injected a politically controversial issue into an English class. Perhaps a better way to put it is to observe that he injected an issue where beliefs depend a lot on tribal membership so to speak. Even if most of the people where the university is located are members of the Correct Tribe, it's still a red flag.

ETA: Besides which, I am skeptical of the claim that "global warming" is uncontroversial in continental Europe as opposed to other parts of the world. (Of course it is unclear what "global warming" means and interestingly a lot of the fervent believers in "global warming" are not able to define the phrase.)

Here is the Wikipedia article on "Climate Change Opinion by Country."

http://en.wikipedia.org/wiki/Climate_change_opinion_by_country

In particular, have a look at the maps in the upper right. It actually looks like people in Latin America are MORE likely to believe that "rising temperatures are a result of human activities" than people from continental Europe.