Devil's advocate, this output could have unexpected results, making a filter possibly desirable. Browsers do filter by default with safe browsing URL lists for malware, and they gate access to sites with bad certificates. But agreed users should have control, leaving such filters as safe defaults only.
> Browsers do filter by default with safe browsing URL lists for malware
Yes, for malware. As in, software created by criminals to damage your computer and/or steal your personal information.
That's not even remotely comparable to what StableDiffusion does here. What they do is refuse to generate content you requested, based on opaque criteria that no doubt are ultimately influenced by quasi-religious sentiments retained from the Bronze Age.
The concept is quite similar to the NSFW filter found on Google and other image searches for many years. Like the “mature” search settings, this filter is active by default but simple to disable.