Doubly so if the restaurant is fictional. 
A semi-factual answer …
IME having eaten half my meals of the last 40 years in restaurants all over the USA and a few other countries …
Simply writing a negative tip might work.
Talking to the server, the cashier, and the manager, in that order, will work. So do that.
According to @Czarcasm’s link, they have to tell you ahead of time.
Yeah, but even then, you can sometimes just ask to have those charges taken off (like in Vegas)
As I understand, the merchant can bill the credit card company for the total written on the receipt by the customer. So if the bill was $37.00+7.46 and the customer writes “-7.46” for the tip and then “$37.00” on the total line, the merchant can only charge $37.00; that’s what the customer signed for.
If they enter any other amount, the customer can contest it and the receipt the merchant has, which he will have to fax (or whatever) to the CC company, will show what the amount they were allowed to charge.
There are plenty of bogus posts out there - surprise, surprise. I see regular posts about how to calculate your tip for your waiter - use 30%. The latest said 40% (!!). There’s regular posts about someone being asked to give up their seat for the poor starving grandmother/child/pregnant lady and refusing; where often, surprising, many of the surrounding seats are empty, almost like this is a movie set of half a plane interior. It’s been decades since I’ve flown on a big jet that wasn’t pretty much sold out. My favourite is the bike-car or motorbike-car collisions, who’s fault is this? Designed to trigger the “blame the cyclist/motorbike” reflexes by being blatantly stupid.
They are all “stupid for clicks”. Presumably, they get paid based on views. The more annoying, the more people will view it and add to the conversation to say how wrong or stupid it is. Worse, some of these are epople stealing someone else’s video and making their own post - seems fitting that people making stupid posts get ripped off by others doing the same.
I tend to tip around 20%, so I just do a quick calculation in my head. Either that, or just double the tax.
I think the 30% (and 40%) was an obviously ploy to rile the viewers and get them to engage with outrage, which generated whatever participation points the poster gets. The point of it all being, provovcative and annoying (and incorrect) tends to be more lucrative for the poster than accurate and informative. Then with all the participation that results, the algorithm bumps that to the top of people’s feeds.
The most obvious such post was the guy who posted “installing hardwood flooring” using a metal hammer to push the planks firmly against each other.
Posting fake outrageous restaurant receipts is another example.
That’s what I was thinking too; I’d probably just calculate the tip I felt like and put a negative amount for the difference (assuming it’s less than 20%). They can’t force you to tip at all, much less a specific percentage.
Pretty common also.