Tips are part of the compensation structure for front of the house staff. You are ethically obligated to tip.
Again, your compensation is between you and your employer. If I don't tip, perhaps your employer should be paying you more. Raise the prices to account for this.
Yeah, the staff would be assholes by any measure. Publicly confronting a paying customer, demanding a tip. I've personally never ever witnessed such a scene. Have you?
I attended church for years without tithing at all. I didn't feel able to. I definitely did not get cornered or lectured or confronted by the priest for my deadbeat spirituality. My own conscience eventually prevailed, as surely a non-tipper's conscience would.
Actually, the receptionist called me once and brought it up in a non-judgemental way, and I was the one who lectured her, saying I was volunteering and contributing an abundance of my time and talent such that I was making up for the $0 tithing. And she noted that down in my record, and the notes were still there when I got her job years later. It was kind of amusing to me, remembered as the guy who mansplained stewardship to the parish office. But I also brought it up directly in private with my pastor, who was unwilling to... command me to begin tithing.
Waitstaff is literally paid to be kind and courteous to customers. Even if they personally obviously hate my guts they are still polite and non-confrontational. There are plenty of non-verbal ways for you to give bad service and express hostility to diners in the food-service industry, that do not involve confronting or insulting them.
The theory is that gratuities reward great service and so a gratuity paid should be commensurate with that outstanding service. I don't know if this is true anymore, because I only adjust upwards in exceptional circumstances, and it's not often that waitstaff goes "above and beyond" in obvious efforts to earn higher tips. Not even in those breastaurants like Hooters.
It is customary for a diner to leave $0 or $0.01 in retaliation for blatantly bad/rude service. It would also be customary to never return, if you're that offended. Surely, if the party did return, the staff would be entitled to treat them rather poorly. They could conceivably refuse service to a non-tipper. But why though? And why in the world "confront" a customer? That will surely earn 1 star on Yelp and Maps.
If a particular server earns $0 tips, rather than confronting customers, they should probably pause to consider what went wrong at that table. The management should take notice if this happens on the regular. Far from confronting customers, $0 tips should generally considered a signal of bad service or dissatisfaction, don't you think? If someone already felt they were mistreated, how does a confrontation address that issue?
(I don't have an opinion on the overall point of "tipping culture".)