Now you’ve just survived a discouraging rejection, and you want to vent. Of course you do, and of course you should. You have writing friends who understand that providing support is part of the process. To them, you can say that the editor is obviously an ignoramus; anyone with the sophistication of a ten-year-old could see how elegantly your plot flows from the characters’ motivtions; that anybody with a brain can see what you did there; that editors just aren’t ready for strong women characters with flaws.
Just be careful where and how you say these things. An e-mail circle is a great place to vent; so is a restaurant, a bar, a coffee place, a walking path. (Probably not at a table in the ConSuite at a convention.)
You know what isn’t private?
I will bet $100 that if you tweet about how ignorant, arrogant and myopic an editor is, they will see that tweet within a day. If you use their name (even if it’s not their twitter handle) they’ll probably see it about an hour. A whole bunch of other editors will see it too, and they’ll see your name, and they will assume that working with you, even if your writing is good and you have some interesting ideas, is going to be problematic.
Every editor has had at least one experience of taking a chance on a work that had good qualities and an interesting idea. Every editor has had at least one experience of discovering, hours (and no story) later, that the writer is more interested in being the protagonist of their own personal drama than in telling a good story. Every editor has wasted hours, and suffered hurt feelings, stress and possibly even mild threats (eg, lawsuits), because of that person.
By tweeting about a mean, nasty, stupid editor who rejected you, you are placing yourself in that category of person, not just for the editor who rejected you (if they remember you or your story) but every other editor reading your comment as well. So don’t to it.
Cultivate writing friends who are going to provide the emotional support you need via e-mail or via a private FB circle. It’s fine to put on Twitter that you’re sad because a story got rejected. You probably don’t need to do more than that. I think if you’re going to vent on Facebook you might want to mark the post to be limited to Friends, for much the same reason; if it’s public, you have no control over where it goes.
Count on your writing friends, and be sure you have also cultivated ones who will be honest with you and who will say, “Well, events do get confusing in the middle of the story,” when you’re ready to hear it.