Mostly find people are dicks on this too. I always fly the alliance flag, shout that I am friendly to other players approaching etc but it doesn't seem to matter. I've had ships flying the alliance flag just attack my ship on sight, and on numerous occasions I've had solo players trying to sneak onto my ship to kill me and steal stuff - one of them ran off with a Tall Tale item trying to urge me to chase after him which was pretty shitty.
What I find helps now is to always play with the largest ship, as it tends to make the smaller ships sail away from me more often (they assume there's a larger crew on board). Also, when on the verge of completing a Tall Tale or loot session, I open the crew up to randoms to help protect me in the final stretch.
Although one time that didn't work out too well when a crew member decided to troll the rest of us by throwing loot off the back of the ship while we were on our way to deliver it to an outpost
I also have a policy now of no mercy for these people. If they strawberry float me over, I spend the rest of the gaming session getting payback
Still love this game though