Unless they tipped $0.01, I'm going to say it was too much, and even then. 5 stars and no tip is
maybe unaware/forgetful. 0 or 1 star and no tip is a clear message.
And who cares if an asshole thinks you're an asshole? If someone is a complete asshole to you for no good reason, don't reward them. This is giving them way too much space to live inside your head. It smacks of a guilty conscience on the part of the victim when it should be the other way around. But in the absence of that, the least you can do is spend your money on people who will do better with it.
There are many shades between someone who is grumpy, having a bad day, in the weeds, maybe doesn't smile but still brings your food and gets the job done well (I've been this person), vs someone that directly insults you while bringing it cold after clearly ignoring you for a prolonged period (I've had this happen to me–guess what? No tip for you!).
I look at the converse situation the same way. I get pissed when places bend over backwards to accommodate customers who clearly are assholes and exploit the fact that corporates will hand out gift cards, regardless of the absurdity of the complaint or the inappropriateness of their behavior. Why would you invite someone like that back?
Signed, waiter in America for 7 years. I was stiffed twice in that time, once by an entire family that skipped the entire bill, the other by a rowdy table I had to cut off from alcohol who then threatened to shoot me after my shift. Once or twice I had some foreign tourists tip me like 4%. Even then, I averaged maybe 19% tips over the entire tenure. Everywhere from dives to white linen tables with 4 different glasses and forks; chains and indie. Never more than $2.13/hr salary.
I've never heard what parent poster said. But now that I have, I must say that I didn't think the foreign tourists thought I was an asshole or incompetent, as everything went swimmingly between us, and I also didn't think they were assholes. I worked with a ton of people who complained plenty about that kind of thing, profiled people, etc. I still wonder to this day whether the family that skipped had some sort of emergency to tend to. It sucked at the time, I wound up having to pay it out of pocket, but in the end I made bank overall. C'est la vie.
That's all to say, the world isn't so black and white, learn how to spot outliers on either side of the average, and reward the good and disincentivize the bad as best as you can. And don't get too caught up in what you think assholes' opinions of you might be.