I think that one of the things that people forget is that the knife attacks we practice in aikido are not even close to that which someone with even a week or two of basic knife fighting techniques would do. Heck, I haven't had any formal knife fighting classes, but I wouldn't attack in the shomenuchi, yokomenuchi, tsuki, and/or slash attacks that we most commonly see trained in aikido. That'd be most silly in my mind...
What we do with tanto attacks in aikido is, in my mind, stylized, just like pretty much everything else that we do. As my teacher says, the only place someone will leave a fist out and wait kindly for kotegaeshi to be applied onto it is in the aikido world.
If you want a bit of "reality" training with regards to knife fighting, give uke a red magic marker and have him or her really try to tag you. Granted, it won't really show how "deep" the cuts would have been, but it's still the difference (as is being discussed in a different thread
) between having good intent in an attack (ie the aikido way) versus having an intent to harm.
This is one of the reasons why I don't see why working with a live blade in aikido is very conducive to anything in reality. It's like walking two feet into ocean so your ankle gets wet and believing you know how to scuba dive.
Just my thoughts this morning.