To be a little bit fair to those people, I have been in many situations where people go "my matlab/python code is too slow, I must re-write it in C", and I've been able to get an order of magnitude improvement by re-writing the code in the same language. Hell I've ported terrible Fortran code to python/numpy and gotten significant performance improvement. Of course taking that well written code and re-writing that in well written C will probably give you a further order of magnitude improvement. Fast code in a slow language can beat slow code in a fast language, but obviously never beat fast code in a fast language.