This is ignoring the fact that sensitive data may actually be inside the (vulnerable, locked-down) process. Or checks inside the process may in some way be infl

This is ignoring the fact that sensitive data may actually be inside the (vulnerable, locked-down) process. Or checks inside the process may in some way be influenced (remember register_globals in PHP? This happens even when you execute PHP in a locked-down container). A safe language greatly helps to prevent the sort of bug that compromises within-process security.