[Assassin]

Wow!! Am I different. About the only thing that will cause me to stop reading a book is if it is just plain terrible; poor editing, unpredictable characters who constantly change emotions, unbelievable plot, too much or too little detail to convey an image of the scene. I wouldn't even start a horror, sci fic, or fantasy story because I don't like those subjects.
I'm not turned off by profanity, detailed sex, or abuse IF it is important to the story itself; ie as in a character study, to drive home exactly what type of personality the character has. Or if it is necessary to show changes over time in the character's behavior. Limiting a writer to no sex, no profanity, no explicit violence, no animal deaths, no, no, no is like tying his hands and feet and telling him to swim.
However, I do agree it is the readers absolute right to avoid issues that turn them off. I quit reading John Sandford's novels because of his injection of his liberal political views. When I want political commentary I'll buy non-fiction dealing with that issue.
And the story doesn't need to have a happy ending for me to enjoy it. Some works should end badly, that can be the whole point of the story. Those simply aren't good reads for people who need positive endings.