What proposition, exactly? If someone does something of which others disapprove, and those others mistake you for one of them, then it would be wise to dissociate yourself, particularly if you also disapprove, and your silence is likely to be interpreted as evidence of association. You don't have to, but if doing so will improve your situation, why would you not if it costs you nothing? Conversely, given the obvious benefit of dissociation from an activity with which you also disapprove and which costs you nothing, why would you remain silent?Ok, so you don't agree with that proposition? Good. Now why do you agree with a very similar proposition wrt Jews across the world and their silence over the actions of Israel?
I think we are talking about rational behaviour more than anything else.