You cant really expect much from these forums in way of support but one thing people won't tell you is that I think just about everyone at UPS goes through what you're going through at some point. Over time, you learn how to deal with it more effectively given that for some, the harassment and targeting never stops.
My recommendation is to be less angry. What worked for me may not work for you but when you drop the anger and not take them seriously, even start making a joke out of how ridiculous their existence is, they eventually do less of it. I'm a stellar employee, certainly not the best but I have dealt with my fair share of what you're going through.
In the end, they're just upset they've dedicated so much of their lives to a company that expects them to pay for their half assed benefits and aren't given a pension. They're not happy so they insist on making you unhappy. Dont let them win.