On the back of writing some fairly solid workaday code in C that was very MS-DOS specific and publishing several books about it he had the unmitigated gall to dare write an annotated guide to The C Language Standard in which he got a fair bit of detail about C the language of the C Virtual machine wrong.
The first level of being a C Guru is an intimate understanding of Your C Compiler on Your OS using Your Hardware. The second level is the self realisation that everything you thought you knew was wrong.
Poor old Herb positioned himself as an expert, wrote a book on that basis, angered the Gods who counter attacked with an annotated guide to what he got wrong and rubbed salt in by coining the term Bull Schildt.
Frankly he did a service by taking a bullet like that as there now exists a kind of Platonic dialogue in which you can read the C Standard, read what someone thought it meant, and then read a commentary on that.
Those C chaps can be a prickly bunch :/