Lots of generalisations here on knife fighting I see.
Good for theory, not so good for practice.
Just a question. How many Aikido folks here practice Tantodori in Aikido where the attacker is allowed to attack with a knife in any way he wants and fully resist your technique with muscle power, positioning etc. and attempt to cut, strike, throw, pin or whatever else he can to you in order to protect himself and not let you get off a technique against his initial knife strike?