I've mentioned this on the forums before, but years ago a woman noticed me using the tiny scissors on my Victorinox Classic SD to snip some paper. She said, "I hope you realize that's a deadly weapon you're carrying." She was serious, and her tone was obnoxious. Now, if there are people who can think a Vic Classic is a deadly weapon (TSA sure does), then it's no surprise that any knife, no matter how small or benign, can be seen as such.
Jim
I think that, to some degree, one has to differentiate between a common perception and an unreasonable person. I once had a guy tell me to "not f[***]ing look at [him] like that or [he is] going to f[***] [me] up."
Granted, this guy was about three times my age and gangly, so I told him "I wasn't looking at you, and, even if I was, I can look anywhere I damned well please in any fashion for as long as I wish. Go f[***} yourself, buddy." He kept yelling threats and I kept walking with a firm middle finger aimed directly behind me.
I'm not some snappy punk kid, but, I don't feel that it's wise to sheepishly react to the unreasonably angry or dumb unless you or someone else is at real physical risk. If I think their actions are uncalled for, I won't reward them by letting them win.
In the situation of being criticized for a SAK being a "deadly weapon", I would probably remind her that her definition of a deadly weapon makes almost everyone around her an armed psychopath (keys, toothpicks, keychains with any kind of heft, earrings, etc), and ask how she managed to not panic all the time.
Actually, that's pretty idealistic. In the heat of the moment, I'd probably just say "Yes, I shall slay thousands of corrugated boxes with this knife without mercy, pity, or remorse."