Just because nothing is completely secure doesn't mean we shouldn't strive to make things as secure as possible.
Should you harden memory? Setup SELinux? Yeah, do those things, those are good meaningful things to do.
Should you prevent users from running apps? Prevent downloads? Restrict third party apps? What about tracking everything the user types in? Tracking every app the user opens and when they open it (eg, Apple)?
What about bypassing user firewalls (Apple again)? That's for "security", right? Forcing your own DNS resolver (Google)?
User hostility is never an acceptable tradeoff for security.