That's not what's happening, this is an old(er) discussion.
pcwalton is asserting in general that modern C++ is not memory-safe, with the goal of promoting Rust and discouraging C++ usage.
Now that assertion is true, but it's not really useful, because programming language choices are not done only on the basis of a language being completely memory-safe. It's also misleading to emphasize only this one aspect (while ignoring others) and to such an extent (complete vs. good-enough safety).
It is concerning that this regex library has security issues. People should review their usage of it. But the original comment is something between offtopic and being inflammatory for the sake of it.
"There are a number of people who feel there is no safety problem"
The thing to remember here is: no safety problem... big enough that one should abandon C++ for Rust instead of working on tooling and idioms to improve it. That's what pcwalton would like.