On one hand, C++ is an incredibly complicated language that one can invest considerable amounts of time into. It also used to occupy a unique niche where you get tons of abstraction features yet as much blazing speed as you care to spend time optimising. Rust is encroaching on that niche.
On the other hand, C is an incredibly simple language, which does not allow for convenient expressions of particular abstractions. If they hated C++ because it was too hard to follow. What the code is doing, they probably hate rust for the similar levels of abstraction affordances.
When I hear the bad faith arguments from people who really should know better, what I hear is a group of scared developers who have been able to coast on their knowledge base for years or even decades, and are now feeling like their skill set is at risk of being unnecessary.
It always seemed like an unproductive attitude to have in a knowledge-based industry like software development. I am also a C++ developer, but you bet I am learning Rust on the side, because I think it's a good idea to skate where the puck is headed. I also learned enough of Zig to be dangerous a few months ago because it was fun.
Either way, I would suggest those developers reflect on the reason why they have this reflexive need to throw a wrench into any conversation mentioning rust. If their intention is to slow down adoption through hostile community sentiment, it's not working.