It is extremely useful to continue asking this question for many reasons, not the least of which being that it is not self-evident to enough people to have formed a stable inter-subjective reality.
If a position can't withstand questioning, then it is a fragile one. There are many questions surrounding the overall good of safe-spaces, and they should be answered, or attempts should be made to address them.
Moreover, the questioning is good for those listening/reading (like myself) who hope to find where the fissures are with respect to both positions, for those who advocate for safe-spaces so their arguments become stronger and more articulate, and for those who dissent who are seeking clarification and exposing potential pitfalls. And perhaps minds can be changed...on either side. This is the problem with facebook--and it's a HUGE problem overall: no one ever changes their minds! Probably because at present it is more valuable or satisfying or whatever to belong to your tribe/bubble than to actually grow.
Right now safe spaces are experiments.
Also, I think it's important to understand that people's objections to it come from a solid belief in equality, not some other nefarious, sinister reason.
It seems to me safe spaces are based on the 'it takes a few eggs to make an omelette' philosophy, and if that's what a community wants to try out, then that's fine (I believe communities should be able to figure out their own inter-dynamics), but there exists this fundamental inconsistency with the social liberal idea of equality (which is also an inter-subjective reality, but one most of us think is noble). It's important to ask if we're squaring that egg only through cognitive dissonance.
And I've been thinking about @edbkt 's anecdote...
Ok, this is going to seem controversial, but why can't those for whom it is a momentous occasion follow the same laws of queueing that teenagers have followed for decades? It says that if you are a superfan--if the event means that much to you--you show up early to get a good place in the queue. That's who should get priority. That's who does get priority as a rule (the exceptions being instances like the one above). I can also understand the break from convention in terms of a marketing strategy, and so there would exist an element of....use-iness in it.