Despite Nye's popularity and willingness to go to the bat for various causes, he loves being in the media. It's how a person like him stays relevant. So while I'm sure part of this is him wanting to defend science, part of it is likely him wanting to be on TV in a "big-ticket" situation that will keep people talking about him. My high school physics teacher was actually somewhat renowned, having been published a few times and through being a part of various science boards, and had the opportunity to meet Bill Nye a few times. Mind you this was back in the 1990s and early 2000s. But from his encounters Nye came across as self-righteous and important, and somewhat egocentric. A person traveling around with a bit of an entourage and putting himself on a pedestal.