According to the Merriam-Webster dictionary, impetuous can be defined succinctly as "without thought or reason; controlled by emotion rather than thought". However, violent is listed as a synonym, when violent seems to be relegated purely to emotions of malice or rage. Impetuous seems to encompass all emotions (can actions done out of sadness/sorrow be considered impetuous?), whereas violent is limited to a few related emotions.
Why are these two synonyms if the domains in which they are correct differ?