That depends entirely upon the context. There are many situations where not tipping is rude. There are also situations where tipping is rude. "Rude" is a quality related to social expectations. You can be unintentionally rude due to ignorance of the norms, and that doesn't necessarily make you a bad person. But if you knowingly refuse to tip when tipping is expected for a provided service, then you're a shitbag.
lmao you could have said coco or diamonds or meat packing or the World Cup or gestured vaguely at the country with the highest prison population, but you had to go with the fictional example. Or do you genuinely think China has slaves driving combine harvesters (unlike Angola or a dozen other prisons where slaves pick cotton by hand)?
If someone is not even attempting to getting the law that allows their core income to come from tips changed that makes one complicit and therefore obligated to tip.
If you are fine with server's primary income coming from tips then you are obligated to tip.