Have you noticed how many of these stories about quitting have (now old) coworkers telling the OPs that they're just exaggerating, making a big deal out of nothing, etc. and to come back to work?
We've seen practically every crazy, unethical or even illegal act there is, many even with evidence, yet the number of times the line “and my coworkers” is used when taking about trying to get them back is uncomfortably high.
Yeah, now that that person is gone you'll probably have a harder time yourself, but is their reasoning that they should had continued to endure the abuse and injustice so their own work life was a little easier?