IMHO, the value of the protest is to demonstrate a portion of the electorate does not agree with whatever they are protesting. There are a lot of people in a bubble that seem to think the majority always views things exactly the same as they do. Maybe you will always default do doubling down on the status quo, but some people will eventually inquire as to why someone is willing to inconvenience themselves to protest. Once someone starts to be curious about other people's motivations and reasoning, it often does impact their own opinions, for good or bad.