I never ship UPS and if I have a choice I choose USPS. I know people who work for UPS.... I won't say much else about that. I have had more things damaged by UPS than any other carrier. I've also never had USPS/Fedex/TracOne blame everyone/thing but themselves when something goes awry and willing to help.
What always pisses me off about UPS is that they never take ANY blame. A perfect example (for those who have Amazon Prime and order through them may understand this). Amazon says "Order within ____ hours to receive it by ______". Amazon has special accounts with UPS - and what they do is tell UPS where a package is going and when it needs to be there by. UPS looks at the distance/ways of travel, and for Amazon, UPS determines the method of shipping (ground, air, 2nd day... etc.... For instance something going 30 miles doesn't need to go by Air if it's 2 day shipping....). Something I ordered was guaranteed 2 day shipping (with a received date). Called UPS on day 2 and they said it wouldn't be there as it didn't make it on the truck. Day 3 UPS said it wouldn't be there, showed up on day 5. UPS claims that it was my fault for choosing ground. When I explained it was Amazon, prime, and guaranteed 2 day shipping, they blamed Amazon. Called Amazon and they said "No, we told UPS it had a guaranteed delivery date of ______, which was 2 days. They chose to ship it ground." The reason it didn't make it via ground is somehow the package didn't get onto one of the trucks it should have (as the truck scan showed within the tracking that the package was going where/when it should have). In any event - UPS failed then blamed it on me, then blamed it on Amazon. As a prime member, and a prime item, Amazon has a 2 day guarantee - and the Amazon customer service verified they told UPS that guaranteed date. UPS will go so far as to say "You aren't our customer, we don't answer to you" if you are the recipient.
With all of that said - a bumper getting scratched that will ultimately get scratched isn't a big deal.... I had a similar issue where a (rare) transmission was decently packaged (granted at 140lbs it should have been on a pallet) was delivered and the UPS guy decided that pushing it off the truck and then rolling the box across the ground was the best way to move it (until I came bursting through the door telling him to just stop and leave it where it was... luckily Toyota overbuilt that beast and it was fine... but what it does show it the normal lack of respect that UPS tends to have. Nobody wants to spend the money on something nice and have it treated poorly. Fact of the matter is - if UPS has a rule regarding large/heavy items then they should have refused the cheaper shipping method that doesn't include the heavy/large factors to handle properly.