"For me, anger is the emotion that says something needs to change, and working toward that change is sometimes expression enough. "

Exactly! "Expressing your feelings" is not the same thing as "allowing your first instinctive reaction free reign". Particularly if said instinctive reaction is very strong and potentially violent. Speaking calmly and reasonably, explaining just how furious you are and why and what you'd like the other party to do about it over a period of minutes, hours or (if necessary) weeks, while only allowing your face to turn puce occasionally at key points, can be just as expressive as (and ultimately more productive than) exploding with said fury on the spot.