@monger-of-war
Sorry, but we have all been there at some point. The first and most important thing to learn in this game is to not put on blinders and focus on PvE aspects. While doing PvE one must scan the seas and spot those sails on the horizon instead of when they are pulling up next to you.
This is a skill I have learned to do frequently enough to keep myself safe and provide the choice on how I will respond. How did I learn how often I have to check? I got rolled up on and murdered... that is part of the game. Instead of whining that I need a cloak of invulnerability, I became a better pirate. One that masters the seas and can sail on their own terms in the safety I choose.
Your friend should have had the best tutorial in the game, a pirate legend mentor: you!
However, it seems like you never learned to actual keep yourself safe. You state you don't want to stick them in the crows nest and I agree. You want to join them on the island, which I also agree with... yet how did you not teach them that while on the island it is still important to watch the seas at regular intervals and more importantly how did you not notice?
There are many people on sloops that are solo. They do not have the choice to have a permanent look out, must gather all their loot themselves and they manage to keep themselves safe. I am one of these pirates and I have done dozens of Athena voyages solo and never lost an Athena Chest, yet have lost nearly every other piece of loot of the voyage during my sessions due to errors in my ways. I have learned, I have improved and now I can sail these seas in safety.
People need to understand that the Seas are not a easy peaceful environment, but a seas where pirates rule the world. Act accordingly, learn the ropes and keep yourself safe. Solo or four man, the tools are in the game.
A sloop does not need a peace flag, the game does not need it. We have 6 ships on a server, if you cannot handle watching out for 5 other ships you deserve what you get. People cannot enter the game as a landlover and expect to be a legend, unbeatable pirate... it takes practice and most people are willing to learn to play a game.
If I can sail in safety alone, I can take anyone on my sloop crew and keep us safe. I have been a tutorial for new pirates and always ended up with treasure and teaching them a little more about the seas. I showed them how they can sail and be successfully at it. It is like solo+ as they can help, but I don't expect anything from their end.
FYI it isn't that I just 1v whole crews, I just ain't that good at PvP that I could do that. It is about making the right choices and above all awareness.