I agree that any and all spoilers should be kept out of the question title. But I also think we should embrace and encourage the use of;
The spoiler box.
There is a reason that this feature exists in markdown, and it's to hide things that people might not necessarily want to see. Like spoilers!
Obviously, we don't want questions that are a spoiler-box and nothing else, but that is still preferable to potentially ruining a film for someone who mistakenly sees something that they didn't want to see.
The downsides of spoiler tags are minimal, taking very little effort to add in a spoiler tag (it's just >! before the text you want hidden) or hover over one to read what it hides, and the benefits are that we don't potentially ruin someones enjoyment of a TV show or movie by giving them knowledge that they don't want or need before seeing it.
As a site dedicated to movies and TV, this seems like something we should care about.