I think you may have a definition of "racist" that differs from how the term is generally used. If, for example, a specific group of people (based solely on race/color/creed/ethnic background) were prohibited by law to posess knives, then yes, that knife law would be racist. But I don't think that's what you're talking about.
"Racism" is just one category under Discrimination. I believe what you are saying, is that some people discrimate against knife owners. Definitely they do, same as towards gun owners. And just like firearms, there is an increased fear level if the knife is tactical/military/weapon-like/black as opposed to a "tool" even if the same thing can be accomplished with both. The fear level also increases with blade length, even though a 4 inch blade can be just as effective a weapon as a 7inch one, and perhaps even moreso because of concealability.
But while "racism" is the not the correct word, there lies the common denominator in all forms of discrimination, ignorance and the fear that it spawns. Just as when one learns about guns, there is no fear of the gun itself, the same applies to knives. The only thing to "fear", if called for, is the person wielding what is nothing more than a tool.
In just about every country there are knife laws and many have become very strict, mostly through kneejerk reactions to incidents of criminal use.
