Is that not what his original comment was addressing though? There are a number of people who feel there is no safety problem, but examples like this are good indications otherwise. Boost is a very fundamental (as in low-level, not as is essential) library in many cases and having memory safety problem at such a level should be concerning.
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.
I don't know how to explain this more clearly: you are trying to enter an established market and "sell" a product based on its safety capabilities.
But your problem is that the market doesn't think it has a big safety problem, they think they can manage it. And instead of recognizing that and adapting your marketing efforts, you're just repeating the same safety pitch with more examples and details.
How has this been working for you, besides antagonizing the potential "customers"?