Every now and then, Matt Yglesias posts a blog referring to a suggestion that the Palestinians adopt a strategy of non-violent protest against Israel. In these posts, the commenters have reached some non-obvious consensus conclusions about weaker parties protesting policies of stronger parties.
How protest in these situations works, violent or non-violent, is that the target comes to calculate that the repression necessary for continuing its policies is not worth the benefit of these policies. Repressing protest requires a level of brutality that is generally uncomfortable and contrary to the self-image of the stronger party, and so there are situations where the stronger party just lets it go.
One surprising conclusion is that violent and non-violent protest each work in the same way and under the same circumstances. The target policy, what the weaker party is trying to change, has to be non-essential for the stronger party. If that is the case, any organized campaign of protest will cause the stronger party cede the demands protested for.
A corollary, also surprising as it developed, is that a distant but necessary party can be a more effective target than the most directly involved party. In the case of the US civil rights campaigns to end legal racial discrimination southern US whites were more invested in the discrimination than northern US whites. Protests that entered the consciousness of northerners, even those located in the south, caused changes in national policies led by northerners who were not as invested in the system of discrimination whose cooperation was necessary for the south to continue the system.
Comparably, governments other than South Africa's did not feel the investment in the Apartheid system that the White South Africans felt. Protests against Western governments that supported South Africa cause those governments to change policies that supported Apartheid, which rendered Apartheid non-viable.
A continuous campaign of protest against the US and European government policies without which Zionism as a political movement cannot remain viable, likely would cause the US or Europe to change these policies. One difference is that US Jewish citizens are invested in Zionism and have disproportionate influence on US Middle East foreign policy. Jewish Americans though, are a small proportion of the US electorate, this does not seem to be an insurmountable obstacle.
Given that both violent and non-violent protest work, human decency requires a preference for non-violence. But in the case of protest against the United States and Europe, there is another consideration. A campaign of non-violent protest is less likely to be disrupted and thereby can become continuous. One-off attacks, such as the attack on the World Trade Center are not effective at changing policy. Many smaller actions over a longer period of time would have been more likely to change US policy.