Why not? It was trained on other people's work.
Second, the use case described in the submission is functional and internal-only, and does not deprive or have the potential to deprive software developers or artists of any lost revenue or recognition. It's purely a reflective experiment.
There's some nuance into the scope of generative AI, which normally Hacker News does well at discussing. But kneejerk "AI art is theft" comments only serve to discourage people from sharing their experiences with AI.
There's another story on HN posted today about balancing money and meaning and one of the top comments is a sarcastic put-down about the AI generate image at the top of the blog post. If the author had used AI to create the web page they'd almost certainly receive similar praise as the comments on this one. Both AI's are trained on other people's work, yet you seem to think even pointing this out is unfair. Very strange imo.
Most of the comments on that submission are negatively and fairly accusing it of being ChatGPT generated: https://news.ycombinator.com/item?id=37779591
That submission also appears to have been flagged/penalized, so yes, people aren't happy with it.
There is a significant difference between using AI for a functional purpose that others can learn from and using AI for low-effort marketing blogspam.
Only thing I've seen was artists on Reddit and Twitter getting angry about the AI art.
I think you mean that artists mostly think AI art is bad, while programmers mostly thing AI generated code is good.
So I could write an article about prompt engineering with AI art and use the headline "I made an amazing art for my blog without ever taking an art class!"
For example:
https://medium.com/geekculture/i-used-ai-to-create-marvelous...
Either way, it's irrelevant to the GP's comment.
None of this is knee-jerk. These systems alienate massive amounts of labor from the people and communities that did that labor. There is a huge amount of risk involved with mass adoption of this technology that most people on hackernews seem content to either ignore or say it's not relevant to the discussion like you are.