I have to disagree with Diceman. American citizens should be able to own anything, whether others think they should or not. It is part of being American. Unlike other countries, we are citizens, not subjects. Citizens can be armed.
I have fiberglass knives. I have titanium knives. I have plastic knives. I study Karate, which cannot be picked up by any sort of scanner. So does my brother. He is a cop, and the local FEMA rep. My wife does, too. She's a fed.
You'd also be shocked at how many bomb disposal and SWAT guys use non-metallic or titanium knives. It is a lot safer for them, due to their job.