It is a question of good manners...
It might be easier to lash out on social media without making the effort or giving the supplier a chance to sort things out but that is simply not fair play.
Life has to be about give and take, helping one another and giving people (and suppliers) the benefit of the doubt - I accept that suppliers can be given this privilege just once but at least do that before broadcasting an issue that might be otherwise easy to solve.
It is just like a hostage situation...
The supplier gets a ransom demand (on social media) he has no option but to try and do the best for his business. He pays up (ignores the facts and publically gives in to the demand), even at the detriment of his other customers.
Anyone who goes public on social media without first trying to get a problem resolved by direct communication with the supplier is just taking a short cut and will only ruin their own reputation in the long term.
The other side of the coin is that suppliers must understand that they cannot leave the most junior staff running front of house. Every single communication with the customers has to be treated fairly and promptly. The one key bit of advice to any manufacturer or dealer is to communicate with your customers and keep them informed of progress on whatever issue is in hand at the time. If you advertise that you have a 48 hour turn around time for repairs then you had better inform any customer after the first 24 hours if that deadline cannot be met and explain why.
Peter