Do you really think so? Have you ever met anyone whose opinion of anti-government protests was genuinely swayed by such a thing?If it was to express anger at the election result, it worked, but probably at the expense of the support of a lot of folk who may otherwise have sympathised with the scrawler.
How insulting it is to someone's intelligence to think that they can't understand that not everyone on a protest supports the actions of everyone on it, or that, in the grand scheme of things, scrawling a naughty swear word is not that significant.
Do you think the protesters can trick people into supporting them by pretending to be nice? Maybe it would be better if they all marched peacefully from one arbitrary spot to another and then listened to a few speeches.