The world is smaller than you think.
People talk to other people.
People move around. Today's intern might be tomorrow's CEO.
There's no need to be anything but polite and professional.
This is a business. (Whatever business you might be in. I happen to be in publishing.)
On a Facebook loop with over a thousand members, even a sekrit or closed group, you have NO IDEA who else is reading your ranty post besides the twenty or so active people who post all the time. You are not talking to just your friends on social media. Ever.
In this world of social media and hacking and etc., anything you say anywhere anytime EVER can come back to bite you.
As my mother used to say, would you be comfortable to hear what you said repeated on the radio? (Since my mother was in that generation LOL.) Nowadays I'd ask if you'd be comfortable to see it repeated on all the many social media channels and late night talk shows until some other, hotter scandal overtook it? If the answer is yes, good and go for it. If the answer is no, then take a deep breath and hit delete a few times.
If you agree to a deadline, meet it. Or else do some good, clear communicating along the way about what's going on and why the schedule might slip on your end.
If you sign a contract, read every word first and be sure you understand it. Then fulfill the terms or else go back and try to renegotiate but do not deliver something that isn't what the contract calls for and hope no one notices.
If a business relationship isn't working for your business (and yes, a self publishing author like me IS a business), then take steps to correct the situation or to end it. Remember, polite and professional...and no ranty posts later on that thousand person loop about how awful person X was etc etc. If you must vent, do so in private to your closest actual friends who you trust.
There are two sides to every story.
Be willing to receive professional feedback.
A burnt bridge is unpleasant but usually not the end of the world. There are always other possibilities!
OK and because this song has been stuck in my head all week while we discussed this topic here at SFF7, here's the classic Mike Curb song from the movie "Kelly's Heroes."