It's very easy for people to take a few examples of behaviors by people from a certain group and apply that behavior to the entire group when they aren't members of that group--despite what the actual statistics show.
An example that happens all of the time in food service is assigning racial heuristics to tipping. A waitress has 2 customers who leave small tips, customer A is the same race as the waitress, customer B isn’t. The waitress dismisses customer A as a generic asshole, but she uses the example of customer B to reinforce her belief about customer B’s race’s tipping habits. The waitresses behavior (even multiple waitresses across multiple restaurants) certainly isn’t proof of anything about any group’s tipping behaviors.
People from hundreds of different cultures will insist that their cuisine is the spiciest and that no one else from any other culture could possibly handle their food--they can’t all be right. Clearly there are a lot of people overestimating their cuisine’s relative spiciness.
When you are waiting tables all day, you're optimizing for two things: tips, and, even more so, limiting annoying situations. A hypothetical server who carries the bias you describe will learn quickly, like, within a night or two, that haranguing their customers about spiciness will result in both worse tips and a lot of extra hassles. In your example, you were so agitated about the spiciness that you even got their boss involved—that's a huge hassle for a server, a big waste of time and something that probably annoys their boss.
I can say from experience that servers do not have the luxury of making decisions based on arbitrary cultural factors. The data is being drilled into them all day, every day, and in all but the most unusual cases, servers will take the path of least resistance to quick turnover and tips. And if you want to deal in stereotypes, don't underestimate the practicality of immigrants.
I don't think you're really interested in a debate here. First you confused me with someone else, I never said anything about anyone's boss. Second you altered the story to make the person who did tell that story look bad.
They didn't say anything about being agitated or getting the boss involved. They said the waiter asked and they confirmed 3 times and then the boss came out to ask a 4th time.
As to the rest of your point, I think you really underestimate the power of confirmation bias, and I dont buy the servers are just too busy to sterotype schtick.
You can buy it or not, but my broader point is that people who have not been servers probably shouldn't express confident opinions about what it's like to be a server. The fact that a wide variety of cultures treat white people ordering spicy food the same way, and that this happens with so much reliability and to such a strong degree, makes it very unlikely that a kind of mass anti-white hysteria is forcing many thousands of people who otherwise have little in common with each other to behave starkly against their own interests, over and over again, day in and day out.
Every job has folk wisdom and heuristics. I worked retail and then retail tech support for years. I've had to deal with plenty of employees who wouldn't listen to customer's preferences because that preference didnt match some heuristic they were using.
They had the same justifications--"They don't really want it, they'll just end up returning it."
Those employees who insited on treating all of their customers like children because of a few bad experiences were consistently poor performers.
Their heuristics were detrimental, but they kept using them because people are very vulnerable to confirmation bias. No mass hysteria required.
Listen to your customer. Give them advice, warn them if necessary, but don't treat them like a child because you once interacted with an asshole who looked a bit like them.
My theory is that servers are the same as retail employees--a small difference in behaviors between groups reinforces preconceived stereotypes, which causes them to overestimate the differences between groups.
Also, you're saying things like "in fact" based on what you think that other people think the frequency is.
If you stop and think, you'll realize that the ubiquity of this "problem" for you is proof that your intuition is wrong, that you are an outlier, that the vast majority of incidents in which the spiciness doesn't suit the patron goes in the opposite direction.
The fact that you get so much pushback is proof that they are right to do so far more often than they are wrong. There's no reason to think that so many people at so many restaurants would be all be mistaken in the same direction and with such an extreme degree of conviction.
And there is something you can do—offer a lot of resistance without refusing so that all but the most stubborn customers who've tied their self esteem to their ability to eat spicy foods don't make the mistake of ordering food that's too spicy for them.