C and C++ require more manual management of memory, and their compilers are unable to let you know about a lot of cases where you're managing memory improperly. This often causes bugs, memory leaks, and security issues.
Safer languages manage the memory for you, or at least are able to track memory usage to ensure you don't run into problems. Rust is the poster boy for this lately; if you're writing code that has potential issues with memory management, the compiler will consider that an error unless you specifically mark that section of code as unsafe.
I think it's complicated a bit by the fact that this was said on stage at one of their shows. I think canceling the tour is a gross overreaction, but with the current political climate (even ignoring the assassination attempt) I can understand some hesitancy to proceed if anyone is going to be associating them with calls for political violence.
All that said... based birthday wish, fully agree with Gass's joke.