That stinks. Sorry this happened Willco; you were fired for being a good manager and sticking up for your employees.

Unfortunately, echoing other retail survivors, I too must say "it was inevitable." Retail just plain sucks.
My stint in retail hell lasted nine years. It was actually a lot of fun the first few years, but as the economy got worse and also as the competition grew, the store began digging its own grave. The worst was during my last year; the "district" manager (this was a mom n' pop retailer; we had 3-4 locations over the years) was this two-faced former-corporate manager guy (he managed a Target for a little while before burning out, I was told) who acted all nice in front you, then behind your back would ask the owners to fire you. I am certain that the fuck-up I am about to explain was his fault, but I got the blame for it:
I was working at two locations at the time. The one closest to me with people I liked, and one 45 minutes away with slacker high-school kids, a bitter store owner (can't say I blamed him with the place going down the shitter), and of course the "dm." Generally I came in either in the morning until the late afternoon, or from the afternoon until closing at this location. This particular day, I was on the afternoon shift. I get there and the store owner is there by himself, and it being him, I didn't bother counting the money in the register. No need to since it's the owner there, right? WRONG. When I close that evening, I am exactly $100 short. I notice in the store log book that they were $200 short the night before, but the "dm" "fixed" things. This kind of thing has happened before, so I don't worry about it and call the owner, who says they'll look into it in the morning. Fine.
Two weeks later I get paid, and $100 is missing from my paycheck. It's because of the money that was gone before. So after doing some checking, I find out that-
-You are not legally allowed to withhold funds from a paycheck. They can certainly
fire me, but they cannot take away the money I am owed.
-The "dm" seemed to be somewhat
fuzzy over whether or not the $200 thing from before was totally fixed. There seemed to be $100 unaccountable from what I can remember.
-The "dm" who most of us already don't like was trying to get me and another guy fired for who knows how long (the owners shot him down every time though. especially because I "brought in customers." Awesome)
So I talk to my father (who is a lawyer) about this multiple times over the phone before the "dm" comes to find out if I want to quit or not after having had it out with the store owner over the phone. My father decides that given my situation, I might as well eat the money and stick it out just a little bit longer. This was because at the time I was waiting to hear if I would be accepted into the JET Program and go to Japan; quitting and looking for work for what could have been only a few weeks would have been difficult.
And as it turns out, like a week after this incident, they called me to tell me I made it into JET. I had never been grinning so wide before when I called that store owner to tell him I was gone. Despite this bullshit, I still ended up staying two weeks longer than I said I would. The stores would later close down completely at the end of the year, but one location got converted into a poker chips/cards retailer, still owned by the same people. I heard from someone that the "dm" was still working there, but that was like two years ago.