I guess that depends on your definition of pacifism.
To say that he would never use his martial abilities, ever, or to condone such use in ANY situation is probably not correct.
I think where we would differ is WHEN he choose to use his force, and in what skillfull manner.
To many, true pacifism is turning your back, or avoiding conflict at any cost. Not sure if this is what you mean. Don't believe O'Sensei meant this.
Most of what we discuss in this and in every forum is where do you draw the line, and how can you more skillfully use yourself to do it with minimium force.
A questions that we will probably ask our whole lives!