I put myself in their shoes. They usually assume that nothing has been done with the vehicle since the last time they saw you. For many car owners, this is a fair assumption. (Not for the likes of us, of course.) Even if some maintenance item is not quite ready to be replaced, they are also assuming you won't be back on time for the next service, which is also a fair assumption for many owners.
I don't get all huffy with the "did you EVEN LOOK to see that I obviously don't need pads/car battery/S-belt/whatever". I just politely decline everything I know is good, I might then ask why the stuff I haven't checked lately needs servicing, or just make a mental note to check it out myself. I usually just leave with only the service performed that I came there for, but on occasion I throw them a bone and let them replace a cabin air filter or something not too crazy pricey.
Now if they pulled a trick like PontiacHO reported, running down the battery and then wanting to replace it, they would get an earful.
The last time I really went off on a service writer is almost ten years ago, when I declined an engine check on a tire purchase... and they checked it anyway... and left the air cleaner lid removed. I noticed the induction noise immediately, pulled over, put it back together, and got on the cell phone to let the service writer know why I would never be back. Tire shops are a dime a dozen around here, no need to remediate a basic competency issue.
A few months ago when I had the teen driver curb incident, I picked up my car at quitting time and noticed the replacement tire was completely flat. I went in and asked them to fix it, 2 guys had to stay late to jack, pull, diagnose, fix, and replace the wheel. I was late picking up my kid, they were late for whatever, and I thanked them for staying late. The issue was a bad TPMS valve kit, they put another on the sensor and it was good to go. That can happen to anyone, no sense in breaking bad and being an ass about it.