The word was properly being used. The definition of triggered is "anything, as an act or event, that serves as a stimulus and initiates or precipitates a reaction or series of reactions."[1] Definitions also change over time, and the colloquial definition of the word seems to be shifting to "Getting filled with hate after seeing, hearing or experiencing something you can't stand."[2]
[1] http://www.dictionary.com/browse/triggered
[2] https://www.urbandictionary.com/define.php?term=Triggered