Can I wear white after Labor Day, or what's the story? Is this really a thing I even have to worry about anymore? I have real concerns taking up my time. On the other hand, I'd rather not have people throw things at me.
Send help, bleach,
Short answer: You can do whatever you want, fashion-wise, as long as you don't try to go into a McDonald's without a shirt on. Long answer: You can do whatever you want, fashion-wise, and probably always could.
What's that, you ask? Aren't you supposed to not wear white after summer's over? Isn't there, like, a rule? Well, it turns out, no one really seems to know how that whole rumor about white and Labor Day got started in the first place, and if there was ever a true rule, it was never followed by all of the people all of the time. (Except for my mom. She followed it religiously.)
Some folks claim that the whole thing was based on comfort and custom. Before the advent of air conditioning, the thought goes, it was just too hot to wear dark clothes from May to September, so people didn't. Also, white was better suited for summer than for winter, because in the winter, it was easier to get stains on your clothes, just from riding around in open carriages or in those terrifying early cars that required the use of driving goggles and protective gloves, even though you were going maybe five miles an hour, max.
The only problem with the whole practicality theory of wearing white is that if it's true, it's just about the only example I can think of where a sensible idea became fashionable. This is why I'm more inclined to go with another theory: Rich people wore white in the summer, when they were vacationing at fancy-schmancy resorts, and had an excuse to swan about in linen and panama hats all day long. Because, as John Steinbeck once said, "the poor see themselves not as an exploited proletariat but as temporarily embarrassed millionaires," everyone else followed suit.
Regardless of how the "rule" gained credence, there were always plenty of people willing to buck the trend. Coco Chanel famously wore white in all seasons, and I don't think we could accuse Coco Chanel of not knowing what she was doing, fashion-wise.
The bottom line, when it comes to all style questions, is that you should do whatever works best for your taste, body, and budget. If wearing white works for you, wear white all year round, and don't let anyone tell you that you shouldn't. Heck, wear exclusively white, and make it your look. You'll look cool, crisp, and clean -- not to mention, distinctive in the sea of black and gray that still crowds the average workplace.
Finally, you mention people throwing things. This is truly the only concern when wearing white after Labor Day or at any time at all. Not because people probably will throw things -- in my experience, no one cares what anyone else is wearing, unless they want to date that person or think they might have seen them on TV. No, the main thing you have to worry about when wearing white at any time of year is that you might get something on it. I am particularly good at dribbling coffee all over myself when I'm wearing white. On the other hand, if I wear black, I usually spill yogurt. You see what I'm saying.
So wear white, carry one of these, and observe the wisdom of our sainted Laundry Guide, who is much, much better at the whole clothing maintenance thing than I could ever claim to be. And remember that you can wear whatever you feel like wearing, as long as it doesn't get you arrested. The fashion police, thank goodness, are not a real thing.