Note: I am not a person with a trigger, so my writing is from an outsider's perspective.
Spoiler warnings are a strange phenomenon. Once upon a time, there was a play called Romeo and Juliet where-in the titular characters' deaths were revealed in the opening lines. Now, we have TV shows that if someone online simply says "character x, though," it's treated like the show has been ruined. Generally speaking, spoilers are plot points revealed out of context, such as a character dying or an unexpected event. People like the surprise and second guessing that can come from big plot twists, understandably. This has led to discussions of recent media to include spoiler warnings to let people know to stop reading or listening if they want to keep the surprise. The downside has been a lot of outcry whenever spoiler warnings aren't included or somehow not sufficient.
Trigger warnings are also strange, but only in that they're usually missing. Because unlike spoiler warnings, when a person triggered has to re-experience a traumatic point in their life. Unlike just learning new info from a spoiler, they are put into a painful and possibly dangerous space. Spoiler warnings are strange because they might maybe somehow lessen or change one's enjoyment of media. They're strange because people are frustrated when they're missing. They're strange because when trigger warnings are present, people also get frustrated and cry "politically correct garbage." How is it that people are wont for spoiler warnings and begrudging of trigger warnings?
We need trigger warnings. If you have ever had something spoiled for you and felt frustrated, do your best to imagine what it must feel like to be triggered. It's not the same, not at all, but it's a path to understanding a stranger's plight. Try before you begrudge the alleged "political correctness." Because that's empathy, and empathy ain't easy.