Technically you are correct: "C is not insecure". In the same way as "English is not offensive"
However programs written in C may or may not be insecure.
Of those programs you would expect a compiler or interpreter, that has been tested in the wild on millions of programs, and so you are more likely to find the security bugs. Also we hope these programs are written by very talented engineers.
On the other hand Joe Enterprise hacking up a greenfield web service for the first time in C ... more likely to have security bugs.
If Joe Enterprise moves from C to Java. Less likely to have security bugs.
However programs written in C may or may not be insecure.
Of those programs you would expect a compiler or interpreter, that has been tested in the wild on millions of programs, and so you are more likely to find the security bugs. Also we hope these programs are written by very talented engineers.
On the other hand Joe Enterprise hacking up a greenfield web service for the first time in C ... more likely to have security bugs.
If Joe Enterprise moves from C to Java. Less likely to have security bugs.