Hmmm, this is odd.
First, in order to learn a language to the level that some of the effects they points out will occur is very difficult, and possibly impossible, without talking extensively with native speakers of that language (or learning from childhood, which seems precluded in the article). However, it is now considered rude to talk with people in their native language because then you are “othering” them.
Second, they say people looking for some political action to take should do this… which means that the people whom they would like to become more empathetic, etc, in their view, would probably not be among those whom they are trying to encourage to learn another language. (Maybe I should advocate that those in search of “political actions to take” should learn French, which I think makes a person more logical?)
(I would also like to point out that the difference in speaking English and Spanish may not hold for all who speak both languages if they did the study with people in the US who are bilingual because their family of origin is Spanish-speaking and their education was in English. People’s “family culture” differs from how they behave among non–family members.)