UPDATE:
So. Turns out Patrick Stewart has eaten pizza before. However, yesterday marked the first occasion when Stewart ate a slice of pizza, he tells Daily Intelligencer. Semantics. Hmmph.
Also, he was hungover, that's why he did it. Also, how did Stewart fool us into believing he'd never eaten pizza in his 72 years of awesome life? Well...
Whoa, wait a second...
Well, it appears further proof has serviced that Patrick Stewart ate pizza during a 2000 interview with IGN in which Stewart prepared a pie for his interview, who happened to be his son Daniel. That's nice. Here's a Star Trek GIF.
New York residents confirm that Stewart's first slice was enjoyed today at Smiling Pizza in Park Slope, Brooklyn.