jbmonkey, I'm not suggesting that you give up your knife and join the PC crowd. But I agree with TX180SX. Take your knife out discreetly, open it quietly, use it, and put it away. Dont display it anymore than what is necessary to complete your task. Dont continue to play with it. You don't need to Ninja Snap or Spider Drop it open. You dont need to wave and snap your butterfly knife open. These types of threat displays jeopardize our right to carry.
Your knife is a tool, so use it as a tool; not as a threat display. People are reasonably suspicious of people who wave large, black coated, tactical style knives around in public. I know I am. But nobody is afraid of a Dragonfly or a SAK if it is used in a calm, responsible manner. And if all you have is your big tactical knife and you need to cut your sandwich, go ahead and do it. As a former Marine, I have pulled out a Ka-Bar in public when that was all I had. But try to be discreet and polite. Smile and greet anyone who notices. Make an effort to look friendly and non-threatening. Dont sneer at people who appear frightened.
You have a right to use your knife in public. People have a right to take their children out in public and not feel threatened. If you respect the rights of others, they will respect yours. A little courtesy goes a long way.