where did you read "very principled non-tipper"?

That’s why I put it in quotes. It’s like the “very principled video game pirate” when, in reality, almost everyone who pirates games just doesn’t want to pay for games. Almost every anti-tipper I’ve ever known here in the states was nothing more than a cheapskate who wanted to save money. Most of them were black and/or white trash.

Given the fact that with tips, bad customers are subsidized by good customers, doesn't that make tips a bad thing?

That part is bad. But as I’ve outlined in another comment, tipping relocates a not-insignificant portion of the transaction from “customer and store” to “customer and server”. That negotiated compensation results in a higher-than-minimum wage, one that cannot be completely eroded by the company targeting cheap immigrant labor. In a lot of areas, tipping also occurs effectively under the table via cash, locking the government out entirely. Admittedly, this last benefit is definitely vanishing. Trump tried to salvage it with no taxes on tips.

Not to mention that they (probably not true, but I've heard it from Muricans) might spit in your food next time if you don't tip to their satisfaction?

This phenomenon, much like dine and dashing, is exceedingly rare. Messing with food is a felony offense that is taken extremely seriously in America. Most food service people are simply too apathetic to do it. The ones who do? Once again, mostly blacks. And they are just as liable to do it regardless.

I'm not tipping 50% or 100%.

You’ve fallen for rage-bait social media posts. The vast majority of American restaurant service workers are making about 15% tips. 20% if they’re good (or an attractive female). Tipping is, as you say, also mechanism for rewarding good service. Bad servers are definitely punished with lower earnings.

where did you read "very principled non-tipper"?

That’s why I put it in quotes. It’s like the “very principled video game pirate” when, in reality, almost everyone who pirates games just doesn’t want to pay for games. Almost every anti-tipper I’ve ever known here in the states was nothing more than a cheapskate who wanted to save money. Most of them were black and/or white trash.

Given the fact that with tips, bad customers are subsidized by good customers, doesn't that make tips a bad thing?

That part is bad. But as I’ve outlined in another comment, tipping relocates a not-insignificant portion of the transaction from “customer and store” to “customer and server”. That negotiated compensation results in a higher-than-minimum wage, one that cannot be completely eroded by the company targeting cheap immigrant labor. In a lot of areas, tipping also occurs effectively under the table via cash, locking the government out entirely. Admittedly, this last benefit is definitely vanishing. Trump tried to salvage it with no tread on tips.

Not to mention that they (probably not true, but I've heard it from Muricans) might spit in your food next time if you don't tip to their satisfaction?

This phenomenon, much like dine and dashing, is exceedingly rare. Messing with food is a felony offense that is taken extremely seriously in America. Most food service people are simply too apathetic to do it. The ones who do? Once again, mostly blacks. And they are just as liable to do it regardless.

I'm not tipping 50% or 100%.

You’ve fallen for rage-bait social media posts. The vast majority of American restaurant service workers are making about 15% tips. 20% if they’re good (or an attractive female). Tipping is, as not say, a mechanism for rewarding good service.