"We know that some of the most successful entrepreneurs in tech have been difficult individuals who did what they had to do to get ahead.",

"We know that a lot of investors, VCs included, will do what is required to make a buck.",

"It's conventional wisdom that being nice is a bad idea",

followed by a singular anecdotal data point arguing otherwise. I'd posit that it depends on the actual business domain. Some are cutthroat and being nice is gonna be a world of pain for you. I'm not doing dry flower arrangements myself, so I wouldn't know. But in my domain (games) being nice bit me on my ass as much as being mean (if that's even an antonym to nice) did.

So, in conclusion, it's a perpetual dilemma, not one-size-fit-all.

EDIT:

The whole article is a bit disingenuous imho. Title might as well be paraphrased as "Be nice or I'm gonna be mean".

Another food for thought - etymology of nice is from Latin nescius, meaning ignorant.