I don't agree with /u/red-crayon-scribbles ' approach to memory safety, but what you're saying isn't entirely true either.
It is possible to manipulate memory in ways that do not conform to Rust's lifecycle/ownership model. In theory, this can even be done correctly.
The problem is that in practice, this leads to the following, many of which were committed by some of the most highly skilled C developers alive, including major kernel contributors:
https://feddit.nl/comment/19388358