Can I bond gas plumbing via gas water heater's electrical connection ground?
The water heater's equipment grounding conductor takes care of its side.
Check the installation manual (example) for your CSST (Corrugated Stainless Steel Tubing; the bright yellow, flexible gas pipe.)  You should be bonding the gas piping at your service entrance to the home's grounding system.  That's what the inspector is referencing.
Some additional information: http://csstsafety.com/CSST-solution.html