Often the best first step to stop something evil is to remove the tools that make evil's job easier. In this case Facebook is facilitating persecution by making better and better tools to filter data on a large number of people simultaneously. If you want persecution to stop you can't just automatically absolve Facebook of responsibility for the consequences of the design choices they make. Sure people should be careful about what they post online but Facebook and the companies advertising on it offer incentives to get people to do it. Past 'likes' will now be easily accessible forever. It isn't only what you've put on your profile, inferences can be drawn based on the information about your friends. If all your friends are openly gay but you don't want others to know you're gay it can now quickly be deduced with a search.