That's a myth. Fiberoptic cables are actually really robust.
So, yes, all the common stuff is pretty flexible, because its plastic.
That being said, I've seen people do some horrific things with copper, and it tends to survive things it shouldn't. But if you treat glass even half as gently as copper wants to be treated, they'll both be fine.
I think fiber gets a bad rep because large multi-strand cables have stiffeners to keep the jacket from kinking, and people assume the individual strands are similarly stiff. They really aren't.
Had 20+db of loss while it was pinched, but after unpinching it and massaging the kink out, it went right back to normal.