Sometimes there is no middle ground and the only neutral solution is to do nothing, which would make that character the proverbial doormat you are so opposed to.
This is my own personal bias showing, but I don't believe that is actually true. Maybe if you were trying to win popular support, and had to gain the approval of others in order to get your "middle ground", then yeah there might not be a middle ground popular enough for people to support.
But in terms of a persons own opinion? Their viewpoint on morals, believes, norms, and principles? I don't think anyone actually feels like a solution is nothing when they talk of the middle ground, there is just the thought of whether it's feasible or not.
I'm asking for a character to express a view in favor of finding a middle ground and being aggressive/not afraid to be abrasive, about it. That doesn't need to translate into actualization or action, as most characters expressed viewpoints never do, but it would be good to have it at least said aloud.
What the middle ground is though is a tougher discussion, as well as what some might consider a middle ground, or even if there is a true middle ground and not simply ground affected by the shades of the other extremes. It's a much harder question then I gave it credit for when I first wrote this.