Do you feel a customer has to respect you. They don't.
But check out your employers Mission Statement. It will say to help the customer. If a customer is disgruntled, then it's up to you. The employee to handle it.
And defuse the situation. Most customers are upset about a product or something they didn't understand might go wrong with a product. Let's just use framing as an example. If you give attitude in any way; ie..
Body language, facial expressions or wanting to argue. The situation will escalate out of control. "I'm sorry" and "I'll look into it"or "I'll find a supervisor to look into it"(EVEN IF YOU DONT MEAN IT OR EVEN DON'T PERSUE THE PROBLEM FURTHER) will defuse the situation. Never show attitude to someone who is already upset.
Human nature shows this will usually lead to an argument and harsh words. Defuse any probable problems. Then after work go somewhere you can relax and voice your frustrations to a friend or even to yourself. Keeping things that bother you inside will just get you angrier and angrier.
Posting your frustrations may help. But if others don't post or post and disagree with your thoughts it will make you even more angry. Remember in the end "It's just a job." There is so much more to your life than this. Your anger over something in your career will eventually overflow into the rest of your life.
I've been in your shoes plenty of times. Don't allow it to control you.
I hope this helps. Or maybe just say "f**k it".