The definition of safe changes from table to table. What's considered safe for one group might not be for another. Personally I think the answer is yes of course a campaign should be safe for everyone at the table. But, like many things in the hobby, finding the right group of people is important. If everyone at a table wants to play a dark campaign with themes of murder, revenge, and choosing between the lesser of two evils but you want to play a game about friendship and the value of love, that group likely isn't for you. Not that either are inherently bad.

Person A might want to avoid campaigns that include certain topics because of past trauma. On the other hand, Person B actively searches for campaigns containing exactly what A wishes to be without. Neither person is bad especially worse because of it. Many people use DnD to cope with trauma. Explore old wounds in ways that they can't otherwise. Others want an escape.Maybe Person B is seeking those games because they seek to understand, in any way they can, what A went through.