If you're a person at risk due to many of the issues described here, you don't belong on Facebook. If you're a domestic violence victim avoiding a dangerous person "liking" the wrong thing or somebody's innocent repost can put you in danger, pseudonym or not.
The transgender situation is similarly tragic, but it's an issue that trans people run into when presenting ID to buy beer as well. We should get states to provide some sort of transitional ID or something.