From what you have said and especially from the article you refer to in The Economist it is clear, that "populism" is a very populist term, and everybody gives it a meaning that helps him or her to label, pigeonhole and selfrighteously dismiss people with opposing views. In other words, it has no permanent meaning, and it gains its momentary meaning from the context in which it is used to clobber an opponent over the head. 
I can get that. But that Francis cannot get it when he decides to use it when addressing the heads of twenty eight states, that is very disturbing.