Yes exactlyThere are unwritten rules as how to behave when interacting with customers regardless if you're selling goods or services. Among those rules is to never ever talk bad about your competitors. As my paternal grandmother taught me: If you don't have anything good to say about someone it's better to keep silent. Personally I have found that a silent, or very neutral response, is fully understandable by most clients and even make them respect you for your integrity. I have of course attended meetings where people have talked bad about their competition and it never fails to lower the appreciation of the speaker and his offer.
So what the seller did was to talk badly about Koraat (me knowingly not a knife maker) he doesn't seem to know anything about and thus making you (and the respondents to this thread) questioning his business and not Koraat.
Just for the record: I do appreciate the two Koraat razors I've got.
One of the things I like about my employer of the past 22 years is their sense of integrity. Part of that is the message that when speaking with customers, try not to say anything bad about a competitor - focus on saying positive things about OUR products instead.