This is what we need, as soon as the teleport screen goes black.
if DestinationSimRating == "Mature"
The area you are teleporting to is rated "Mature". Mature areas may contain content which is violent, sexual, or may otherwise be offensive to some viewers. By clicking "Continue" below, you agree that you are 18 years of age or older, and are of legal age to view such materials. If you do not wish to continue, click "Cancel".
If the screen is not answered within 15-30 seconds, the teleport should cancel. Additionally, we need a banline around a mature rated sim (anyplace it touches a PG sim) of some sort that when collided with, will trigger a black screen and a similar message. (to cover walking-flying traffic.) once "agreed" to, the banlines can permit entry. Also, when a region goes down, people can no longer be "automatically" teleported to a Mature sim.. and "login to sim by name" is no longer a function that can be used. (please remove it from the client).
As a computer software developer, you have a certain social responsibility to at least conform to the "Rated M for Mature" guidelines. A simple disclaimer, mirroring the "Rated M" text, would go a long way towards insulating your adult content providers from harm (since you do not give us proper entry control abilities to do so on our own.) Since you no longer are willing to take responsibility for controlling minor access to the grid at large, we now need you assistance, Linden Labs, in controlling Minor access to Mature Rated areas of the world.
You could have done more to stop them at the gate. But you elected to no longer try.