Continuing on the topic of vigilantes, could a real-life Dirty Harry reverse the trend of Americans getting softer on crime, as detailed further down? Probably not, and two classical series of experiments about conformity suggest why.
In the Asch experiments, a test subject was shown two lines, one clearly longer than the other one, and asked which was longer. The twist is that he answered last, after about a dozen others said that the short one was actually longer (they were in on the experiment, not true test subjects). After hearing so many other people say the short line was longer, most people conform and say so as well, against their initial hunch. Maybe those other respondents saw something I didn't, or maybe I just don't want to stick out.
However, when there was even a single person from the fake subjects who told the truth -- that the long line was longer -- it canceled out the conformity effect, and the true test subject agreed with who they must have seen as the lone voice of reason. "Phew, so I wasn't the only one who thought so!" All it takes for the individual to rebel is to witness even a small potential group of like-minded rebels. This is value-free, of course: we could be talking about the criminally inclined who, while conforming to the norms of obeying the law, are on the look-out for signs that others are exploiting others and getting away with it.
The same result was found in the Milgram experiments, where the true test subject kept giving increasingly dangerous shocks (or so he thought) to a fake test subject, as punishment for answering test questions wrong. There was an authority figure who gave the true subject the orders to shock the fake subject, and while some aspects of this figure affected how willing the true subject was to give harmful shocks -- such as how near vs. far he was standing -- the single most powerful variable was the presence or absence of another (fake) subject who openly rebelled against the authority figure's orders. Just as in the Asch experiments, the full weight of the authority figure was blasted away by the individual witnessing even one other person stating out in the open that it was wrong, openly defying his orders, etc.
By the time Dirty Harry came out, crime rates had been rising for just over 10 years, and they would only get worse, peaking finally in 1992. In that context, the mass of the population were growing more discontent with how the authorities were handling the crime problem, as revealed by their attitudes from the General Social Survey reviewed in a post below. Seeing Dirty Harry on the big screen, or reading about Bernie Goetz in the newspaper, was confirmation to the average person that they were not alone in wanting to strike back at the hoodlums, and this emboldened them to seek tougher crime policies. I wish I had data on how short of a fuse the average person had when someone slighted them back then.
However, during our era of plummeting crime rates, fewer and fewer people feel angry about criminals; the days of "nothing is too harsh" are long gone. Therefore, a real-life Dirty Harry these days would not serve as a catalyst for a widespread backlash against the establishment -- the average person has to have a shared mindset with the rebel in order for the latter's example to provoke a broader chain reaction. In the Asch experiments, if a test subject had screwy vision, maybe he would truly believe that the short line was longer -- and thus not be stirred by the rebel respondent who stood out among the others in saying the long line was longer.
So, it does give hope that when the population is prepared for it, even a small rebellion can ramp up in a faster-than-linear way, as each one of the witnesses to the original act can start their own little rebellion, which in turn can be witnessed by many others. In this way, it grows incredibly quickly like the spread of a rumor where each person tells several others. "Hey, did you hear about that guy who stood up for himself on the New York subway and shot those parasitic little fuckers?! So it's not just us who's been thinking about doing that!"
At the same time, it should make us more realistic when the population is growing more and more resistant to the idea that the bad guys are bad -- that instead they are "disadvantaged," etc. You can't lead by example if the audience doesn't feel like paying attention. But as we saw below, attitudes can cycle up and down, so you can always bide your time until the next wave of violence makes people more open to treating criminals as exploiters rather than as victims of noxious social environments.