Oh, I agree on those... and those stress me out, too.

List something for "$300 firm" and you'll invariably get that person who says "I'll give you $100 for it" (and not because they're trying to haggle you down, either). My folks actually negotiated down the price of the first HDTV we owned, but I think that era's over now that the internet makes it patently easy to see who has the best deal.
And that last bit is why I don't like negotiating in many cases. It's 2020, we shouldn't have to arm wrestle a sales rep when the internet exists! Of course, the challenge is ensuring that car makers keep prices semi-competitive if they do go to online ordering, rather than just making dealer-style markups standard.
In my opinion, negotiation is for unique offerings and services. When I'm working with our partners and we're orchestrating a deliverable with lawyers in the room, you can bet all the group's finance guys are running numbers to determine the best mutually beneficial profit potential for us, for our partners, and maintaining our appeal in the market. Those negotiations that I'm part of make total sense.
For a car? Of which they're making more than a quarter million of them that year alone? No. That's not special in the slightest. There is absolutely no purpose to it except to get people who aren't "game" enough to deal with the system to subsidize those that are. For cars of which there's literally millions produced every year it's just silly.
When I bought my Subaru in 2015, I went to 8 different dealers across 3 states from their e-sales that had matching cars (because again, there's nothing special about buying an econobox). I had each of them give me their lowest number and noted that I'd only be working over E-mail, and I'd be buying whichever vehicle had the lowest price, because they're all the same. Subaru Impreza, Hatchback, Eyesight, Leather, Climate Control. Check all the boxes and get back to me with the price. I then would tell them where they stood in pricing compared to each other and went through all of that over about 3 days until only 1 remained. And I went and bought the car. Was that easy? Yes (because there's nothing special about buying a car). But it was completely an unnecessary waste of my time.
When I bought my Tesla, I customized it, and bought it just like buying something off Amazon. I paid the single price that Tesla has calculated with the best balance of profit margin and competitiveness in the auto market, and I did it in 15 minutes at my computer.
Even the delivery portion was massively better. With the Impreza I had the car I wanted only after sitting there for an hour with them going on and on about how I needed to buy extra services for it. The Tesla I was there for half an hour spending the vast majority of the time signing forms. Then I'm walked to my car, given a brief overview, and told I'm free to go at my leisure.
I can't wait for Tesla's business model to freakin' crush the auto industry.