Let’s assume that the likelihood of a successful revolutionary overthrow of an authoritarian regime depends on how many people are involved in anti-government protests. (That’s a reasonable assumption, given the fact that mass opposition can grow so wide that repression becomes too costly. We’ve seen that recently in Egypt and elsewhere. See also here). If that is correct, then political freedom and respect for human rights (the latter almost always resulting from the former) depend on large numbers of individuals participating in protests. (It also depends on many other things, obviously. Democratization is a hugely complex process).
The next question is then: when will large numbers of individuals actually participate in protest and a revolution? A single individual will decide to participate after he or she has analyzed the possible costs involved. One element of the cost is the chance of being arrested, beaten up by the police or getting shot. The more people participate in the protests, the lower the probability for each individual of incurring this cost. It’s simply less likely that you get arrested, beaten or shot when there are many people surrounding you. In order to get many people involved, it’s therefore important that every individual has the impression or conviction that many people will be involved. This conviction can be encouraged by social networking websites, such as Twitter or Facebook. Communication about the protest through these media helps to spread the conviction that large numbers will be participating, which will encourage large numbers to participate.
One could argue that something similar happens in cases of racism, discrimination or bigotry. For example, when large numbers of gays and lesbians are allowed to marry, people who initially frowned upon same-sex marriage are now confronted with lots of married gay couples and may start to realize that their initial fears were unfounded. On the other hand, the close proximity between slave holders and large numbers of slaves didn’t reduce racism. Likewise, a larger number of immigrants usually – but not always – leads to more widespread and more intense anti-immigrant feelings rather than less.
Something more positive happens with the numbers involved in gendercide. When the number of sex-selective abortions reaches a certain point, the remaining women may start to escape their inferior position which was the original cause of gender selective abortions. They may do so because their bargaining power will increase: the gender ratio is now 1:<1 rather than the natural 1:1, and men – the majority of whom will still want a wife, I assume – will conclude that it’s necessary to make concessions to women as a means to gain the upper hand in their increasingly competitive struggle for mates.
When reporting of rape is taboo, rape will remain common. But when more and more women start to report rape, the stigma will move from the victims to the perpetrators. Also, when large-scale reporting makes people aware that rape is a widespread phenomenon, women will increasingly adapt their behavior so as to limit the risks. On the other hand, common knowledge of the widespread occurrence of rape can give (certain) men the impression that the practice is normal and acceptable.