People in this country (and, I suspect, many other Western countries) are conditioned to expect a very conciliatory attitude from front-line customer service professionals. It's not the oft-quoted "the customer is always right" - as a lot of the time they're not! - but in most cases, the person serving you is expected to be friendly and helpful, and when they have to give you bad news they're always apologetic and eager to try and mitigate any loss or damage caused to you.
A lot of things that we get from the USA isn't good, but one thing we could really do with is the way they do things there when it comes to customer service.
Front line staff will always aim to be friendly, polite and show courtesy to everyone - but there's also a line that cannot be crossed before they'll switch.
We seem to have lost that bit here (or never got it), where you can by all means complain but you must still show respect to the person you're talking to. Staff in the USA won't tolerate abuse, and will clearly stop and refuse to talk to you any further - and call security if necessary (and in the case of an airport, security WILL respond). Simply swearing is often enough, and they would appear to have the backing of their bosses too - so no fear of reprisals later on.
The result is that most members of the public won't do what happens here and start to argue with staff, accuse them of being jobsworths etc. In fact, trying to do so will just single you out as a troublemaker, and nobody around will be on your side.
Posters saying that staff should be able to be treated with respect are a total cop out, and ignored. The only way to get the message home is by enforcement.
I've made complaints but always remained polite. A good trick is to get the person you're complaining to on your side by making them want to help you, as your complaint isn't really with them but other people in the organisation.
When I've messed up, it's better to confess. Like when I've been done for speeding. No point trying to be clever, just take it on the chin and get on with things. It's a shame a lot of people cannot own up to anything and think that the best defence is a good offence.