Things that emit thermal radiation are not radioactive. An easy way to conceptualize it for stuff here on Earth is that radioactivity involves stuff flying out of the nucleus of an atom, while other forms of radiation do not.
But that wasn't the point being made here. The point being made with the hot spoon example is that EM radiation doesn't make other things radioactive (except insofar as it heats things up). This is equally true of gamma radiation as thermal radiation. Thermal radiation and gamma radiation can both cause harm directly, but neither will make other things radioactive.
That's why it's completely safe to eat food that was sterilized with gamma radiation intense enough to kill you outright.
Here's an example:
"Photonuclear production of medical isotopes 62,64Cu using intense laser-plasma electron source"