From a politics standpoint that is completely true. Which would you rather tell your boss:
Q: Why is the website offline?
A: One of our sys admins accidentally deleted it.
OR
Q: Why is the website offline?
A: Some nation-state/teenager launched a sophisticated cyber attack, we need to increase the cybersecurity budget. It's the wildwest out there!
Mistakes are normal course of action at a corporation. Sane managers will understand that is not possible to not have people make any mistakes. Mistakes are part of the learning process.
Now, when somebody makes a mistake what I am looking for are:
Does this person show good judgment? Were precautions taken by the person reasonable?
Does the mistake show pattern of abnormality? Some people seem to attract failure, maybe there is some underlying cause?
Is the person learning from mistakes? Learning is expensive, if somebody made an expensive mistake I want as much learning as possible for the expense.
Is there some kind of external factor that made the mistake possible or more likely? Usually it is possible to improve the environment to reduce the number of mistakes.
As to preventing these guys from scanning ever again, that is bad decision because it is likely they would never make the same mistake again. What's done is done. The scan showed there are problems with the app, now we should want to know if there are more problems but without risking the application stability (too much).
---
-- Do you know what the Big Co. pays when they pay high salary for an experienced engineer?
-- They pay for all the mistakes he/she made at her previous place.
Usually, HTTP servers would be huge bloats of configuration running on huge machines. As a sysadmin, it was not typically feasible to replicate the configuration on the local machine.
With a static website nobody would figure you can accidentally actually do something harmful to the website. The worst thing that could happen was that you made a configuration error in which case you just rolled back the config.
Of course we were supposed to have backups in case the server failed. While the servers would typically use RAID arrays we knew it would not save against rm -fr so there was a backup but backups rarely could be restored instantly.
Seems like management believes it is better to wait for real bad actor to purposefully destroy your site than have it done by your honest employees by accident.
I know security in 2001 was much more lax (I started in 2000) but this still shows ignorance of management.
The right way to handle this would be to ask your staff to ensure it is possible to restore services and to ensure you know what the tests are doing before you run them.