This is my second time to post a true story. The first one was also attacked by a knife. It was one of our sensei.
I must disagree with your reasoing.
Firstly, you cannot judge the success of one person in a situation as vindicating the effectiveness of a martial art.I have seen a karate instructor get the crap kicked out of him, but I wouldn't consider karate to be rubbish
If this holds true then we can never be certain about all the other MA. A lot of MA people had been beaten before. For example an Aikidoka killed here by a robber. Shot in the head by a .38 caliber gun. A TKD guy mauled almost to death.Yet I know two TKD guys who were able to defend themselves against their who would be robbers.