Yes, the Stoics carefully distinguish between voluntary and involuntary feelings of anger. This is a complex question because modern cognitive research shows that people tend to be very confused about what’s voluntary and what isn’t, especially with regard to their thoughts and feelings. We actually need to train ourselves properly to clearly understand what’s automatic and what’s deliberate in our anger. Deliberate anger is absurd, for Stoics, and irrational. Automatic anger, is morally neutral or indifferent. What matters is how we respond to it, i.e., what happens next.