Well i wouldnt really say its a COMPLETE myth.
im a pretty mellow guy and tren turns me into an award winning *******. Trenbolone does this to a lot of people, along with some of the other more androgenic steroids.
for me it is a throw up between trenbolone and m1t for the worst mood altering steroids. it is subtle, and hard to notice at first. little things will annoy you that never really bothered you before, but eventually you will realize it is a particular steroid you are taking and at that point it becomes an issue of self control.
unless you have a mental predisposition to violence and/or anger issues, recognizing and controlling this possible side effect wont be a problem.