Agreed: Protesting by vested political parties can be enormously effective (e.g., the Berlin wall). But I know of no historical instance in which religious groups have ever been toppled by "peaceful" protest.
In fact, these protests may even unintentionally serve the interests of the target religious group (e.g., feed religious convictions that protesters are persecuting the group in fulfillment of Biblical prophecy).
One of the main reasons I prefer the cool detachment of only speaking to JWs who approach me is that any univited approach by me to them is inevitably perceived as persecution in line with their literalistic take on scripture. I want no part in unintentionally bolstering their self-serving convictions. Besides, non-engagement in protesting does not mean I remain silent; but when I speak, I want it to be as effective as it possibly can be.