What if, somehow, there was a guarantee that the code can't harm your machine -- would you use it then?

This isn't a joke.

It's not just about harming your machine - it can harm your* data, or data passing through your* system!

* Where "your" can mean you, your employer, your customer, another company, etc.

What if it can't harm your data, or data passing through your system?

What if it can't harm anything.

How could a system that executed arbitrary code ever make such guarantees? I mean sure, if there were a magical thing that only ever produced correct code for what you wanted to do I guess people would use it.