I hate Facebook, but I think they are right about this policy. 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…
What is this, the 18th century?
You claim to only be suggesting opsec, while ignoring that such extreme opsec (aka, not participating in many aspects of society) wouldn't be necessary if Facebook didn't insist of removing privacy (aka "the effective capacity to misrepresent yourself").
The power of the internet is that it lets you publish what you want, when you want. This should enable people to act like their true self or seek the support of others. Facebook seems to think that these are bad things that need to be prevented by forcing everyone to id themselves.
Blame Facebook for creating this hazard instead of blaming the victims for wanting to participate in social activities like a normal human.