I guess what it comes down to is...
Mugger comes up to me with knife - asks for wallet. I choose not to run, and confront him, and I end up unhurt and retaining my wallet. Am I a bad Aikidoka because I didn't run away when I could have?
No, but you are probably a stupid Aikidoka. There was a guy in New York during the 60's, I think, who had his car broken into. He got in the car, confronted the kid and was gutted for it. He died a third dan.
The problem is that you are playing the odds. In the first case, I don't know many second kyu's who are going to take a knife away very often. Probably well under 50% of the time. You may be different but no matter who you are you are still playing the odds. Give me enough lives and I'll take out any martial artist on the planet. Eventually, they'll slip, I'll get lucky and they die. The price of losing is too high and sometimes the price of winning is very high too.
By the way, I don't think this is an example of a bad Aikidoka. If we were so good we could take the knife everytime, then we should do it and escort the misdirected individual to jail.