Define "safety". If safety for you is a complete absence of any judgment or conflict, there is no such thing.

Even in the most caring and trusting relationships there are conflicts, criticisms, misunderstandings and that's how it's supposed to be. Otherwise, it'd be a paradise on earth and we wouldn't be able to learn and grow, because the only way to learn and grow is through dealing with challenges and painful experiences.

Safety is a relative concept. It does exist in genuine relationships where people don't feel pressured to play social games, but it has limits in every relationship. I feel safe in my marriage to be completely who I am. My husband accepts me with all my crappy traits, which doesn't necessarily mean he is happy with whatever I do. The same goes for me. I accept him for who he is, even though some of his character traits drive me nuts. Each one of us has defined our limit of how far the acceptance will go and so the safety goes with it, it has the same limit. So far, the space within that limit has been large enough for both of us to feel comfortable and "safe" in the relationship. But every now and then, some of us does something that crosses that limit and then we have a conflict, which usually gets resolved fast because we've learned how to work with it.

So, the point is that relative safety is necessary for a relationship to work and it's important for each person's well-being, but no one can expect absolute safety. We live in the real world of real limitations. People will always have limits of how much they can or are willing to tolerate. It's best when they can talk honestly and openly about it, because then it's much easier to resolve conflicts, to get what you need or to let go of the relationship that doesn't fulfill your needs.

Applying this to therapy, I hate it when therapists say that they provide a "safe space" because it's an utter lie or just pure ignorance. No human being can guarantee a complete safety in a relationship with another human being, so people should stop deceiving each other, whether they are therapists or not.