Ahimsa can be a first tool to fight an enemy as gandhi did against the colonial british, but later the tool became an end in itself, a goal and a philosophy replacing everything else.
We need to know the people or party (or enemy) that we are dealing with better, also we need to have a very good understanding of where we are coming from, otherwise the interaction gives results that are strange or unexpected. So, educating people better needs to be a primary focus.
The question is what is the strategy against a non-friendly opposition ? You can use ahimsa if that is going to bring a better awakening. If the other person is an enemy or behaving unfairly or selfishly and aggressively, and, he is actually counting on you to be non-violent or nice, so that he can get away with doing cruelty to you easily (and even get you to keep quiet about it, say, citing confidentiality or other fear factors like bad recommendation, - as managers often do to honest and highly capable indian workers here in the usa also), then being ahimsa-quiet about it is timidity.
If you can be strong enough to at least tell the truth, and, stronger enough to act or complain appropriately (dharmically), at least you would be known for that courage, and unwillingness to bow down to cruelty. If not, ahimsa may give you a sense of weak survival.
Truth and dharma are the highest values or ideals, ahimsa comes later, as a value in any social setup. In an already dharmic society, it is possible for ahimsa to be the next ideal, this may have been the case for mahaveera, and, buddha. But, when muslim invaders came, ahimsa meant there was no viable enough defence, and, what followed was terrorisation, murder, blood-bath, conversion, surrender, subjugation, inferiority complex, reactive and stressed behavior which became permanent part of the psyche.
As a fighting strategy, ahimsa can be a first weapon, as gandhi may have initially intended against the british, to unite the people of india, and, to twist the conscience of the british rulers.
he was also trying hard to work against the divide hindus and muslims strategy of the british.
But the british made jinnah and the muslims equally important as gandhi and the hindus, created a good divide, turned muslims into enemies of hindus, gandhi was not able to get himself and the hindu nation out of the ahimsa high principle strategy, hindu leaders had become too-conditioned by the ahimsa spirit of the freedom struggle, gandhi used ahimsa everywhere to fight for muslims against hindus also thus spreading a feeling of helplessness in hindus.
After independence, once again govt was against hindu people, govt served politicians, people felt helpless because they were now expected to behave ahimsa way with everybody and everywhere, nation building suffered, govt did not speak up and work for fairness for hindus in pakistan, and did not represent hindu sentiment and it worked opposing hindu interests in india.
Understand the enemy, know what you are up against, and, fight effectively. And, as a society, stand up for truth and dharma as the highest in the heirarchy of values. In a war, everything needs to be considered, examined, judged if it is a viable tool or not, who is the enemy and what are their tools, what are our tools ? what kind of fight and what kind of result do we seek ?
Are they using us against ourselves, to hurt us (as the west uses our own hindu media people against hindus, our own doubts, egos, biases can be used against ourselves by the enemy, as the management here uses our own strengths and weaknesses politically and psychologically against us to prevent us from advancing in our jobs).
It may not be fair to blame just one person like gandhi or nehru, or buddha and mahaveera for that matter, what happened to the others, why did they not speak up, why did they not offer their leadership services ? why were they just following meekly, as they are doing even now ? are they lifeless or selfish or timid that they will blindly follow ?
So what is the solution ? what is the role that each one of us can play to bring about that change ?