Earlier quoted context omitted.
If the second city has ~36500 times the population, then it's not a change in degree at all. City A is no more or less safe than City B, nor is the police force any more or less effective, etc. There are billions of people on the internet now. How many were using it in the days of Usenet?
By a frequentist analysis, which omits complicating factors and may lead to inaccurate conclusions. One obvious thing that a frequentist analysis misses is that the larger the population, the bigger the size of the gang you can summon to harass someone. Getting trolled by 3 or 4 people on Usenet was annoying, but today someone can find their Twitter feed flooded by hundreds of people. The frequency of the harassing a…
If everyone is exposed to everyone at all times, then everyone is endangered in large groups (seems obvious) even if no one is consistently looking for trouble more than anyone else. If that the qualities that inspire that 1% reaction have a clumpy distribution (either in perpetrator or victim), the experiences that individuals have will be vastly different in an average forum, and when holding the tolerance for danger constant, the least targeted will feel comfortable in far larger towns than the most targeted.
Of course, in real life, the larger the town, the higher the level of anonymity. In the case of internet forums, however, 1) smaller groups are being eliminated in favor of larger groups due to finance and economies of scale and 2) there is a profit motive in de-anonymizing users. There's absolutely no degree of moderation that can make it work. Anonymity simply makes the problem disappear. What you said can be targeted, you yourself cannot be.