Its important to be able to talk about whatever is on your mind, be heard, and not be judged harshly or stigmatized for doing so. The more worrysome or taboo the topic, the more important being able it will be to get advice, feedback, and just get it off your chest.
Friends and family are the most obvious choice, but they might have limited time, not be the best guide, or not be understanding on a given topic. Therapists do this for a living, but finding a good one for your needs is damn hard, and cost and availability can be issues. Random acquaintances carry increased risk of alienation as well as awkwardness in asking, but also less burden of worry about the relationship.
In [my] magical fairyland utopia, discussing any topic wouldn’t carry serious social risks and stigmatization. There’s certainly issues with time, place, and manner of bringing up a topic, but making any idea or thought completely “off limits” relinquishes one’s ability to cooperatively and consensually address the idea.
And man, holding something heavy in weighs on people, and hurts that person in so many ways, and by extension everyone’s lives they touch.