There are some people that probably get to worked up about it especially on the internet as you said. But in a professional environment where you have deadlines

There are some people that probably get to worked up about it especially on the internet as you said. But in a professional environment where you have deadlines and a budget you don't have the luxury to be a language purist. You have to use libraries and choose from whats available and whats the best choice often that means mixing C and C++. I'm not saying that people necessarily like to code in C if they prefer C++ or the other way around but they will often have to. And so have some competency weather they like it or not.