I also have distinct memories of watching the Alien meal-time scene for the first time, and to my eternal regret, I spoiled it for myself by having advance knowledge of what was going to happen. (Aside: How many people here really saw it for the first time without any prior knowledge whatsoever?)
Anyway, I'm going to suggest that that case is different because the audience has an inkling that something isn't quite right with Kane, even if he seems to be fine. And when he pops, the logic for it immediately clicks into place. IOW, you can deceive an audience with misdirection (without incurring their wrath), as long as you plant a foreshadowing, or some sort of advance set up or clue (that at the time, they hopefully won't identify as such) that gets paid off at the surprise reveal. That way the surprise makes sense.
For example, Aliens takes a right hand turn in the 3rd act by presenting us with a boss enemy in the form of the Queen, much smarter and more formidable than the previously encountered drones. Which is a surprise, but foreshadowed by earlier conversation speculating of something's existence, and therefore slots right into the story's logic. If that conversation hadn't been there, I don't think the Queen reveal would have worked as well.
TC