Yeah, I think pretty much everyone who has unusual triggers is aware that their triggers are unusual. "Content Warning: Drowning" is likely going to be something someone with a problem brings up beforehand or does what @Pyrephox described above. They aren't going to get mad about it.
Now, if you casually drop sexual assault on your players without explicitly asking how they feel about such things? Yeah, you're a shitty person.
Despite how the "anti-SJW" crowd likes to portray folks, people who request trigger warnings are for the most part extremely reasonable people who happen to have experienced something really upsetting and would like to avoid experiencing it again.
ETA: gotta say @Derp I was surprised at your response, because
@greenflashlight said in Sensitivity in gaming:
because compassion is a resource you limit to immediate friends and family.
is definitely how I also took it. I hope I'm wrong.