You know, I think it's worth pointing something out about the word "safe" given the sense it has been used in lately. In this case, it means people feel safe to express dissent. Not "safe from dissent", as the term is often used nowadays.
Of course the two usages shouldn't be overlapping much anyhow. It shouldn't surprise anyone that a team where people actually attack each other's personal identities is not going to be very effective! But it's still worth pointing out the two very different ways the term can be used, and important not to accidentally substitute one definition for the other.