Whenever I hear someone complaining about the idea of a fellow gamer being upset by something occurring at the table, I think the above. “That person is someone who has never lost anything of real importance in their life. That is someone who is lucky enough to never have experienced crippling physical or emotional pain.” 

Anyone who has experienced real loss and pain should really know better than to belittle someone else’s pain and suffering. So, logically, they’ve either never cared enough about anything to feel pain or they have never lost anything they cared about. Or they’re some kind of sociopath who can’t understand the concept that other people have feelings as real as theirs. 

Getting upset over the idea of setting boundaries and finding out where the line is drawn just baffles me. It’s a game: the sole intent is to have fun. Finding out what the players enjoy and don’t enjoy should always be the first thing a good DM does. And they should always be asking what the players wanted to see more of and wanted to see less of. They don’t enjoy mystery investigations and find them boring? Don’t write an adventure that’s a whodunnit. They get creeped out by spiders? Then use the other 419 monsters in the Monster Manual that aren’t related to spiders. They love puzzles? Include more sealed doors and chests that feature brain teasers rather than simple locks. They’re uncomfortable with sexual assault or violence to children? Skip those plotlines. They hate being railroaded and having their agency taken away? Make sure every plot line includes consent and sandboxy options.