I generally consider myself pretty neutral when it comes to movie and TV spoilers. I don't actively seek them out, but knowing what's going to happen hasn't stopped me from enjoying a movie when I do come across them.
However, it's no secret that a lot of people take them incredibly seriously. I know a guy who actually got into a fistfight with a friend of his because they were careless enough to spoil Game of Thrones on him.
Still, I'm not sure even my buddy's level of intensity about this can match the long con one seriously enraged Avengers fan pulled off.