We all know it's not fun to loose. Even pirates don't have fun loosing. If you're not able to defend yourself, there are some things you may give a try:
- short trading routes
-> ie. Erie (Passangers) to Manhattan (Liberty Ale) and back to Erie
- hiring an escort
-> ask bounty hunters or house security forces or freelancers to join your journey, 250.000 Credits per gate are fair
- negotiate with the pirate
-> scan him and watch his cargo bay, you don't need to give him more than he can carry
-> maybe you can give him money instead of your cargo, but give him a fair amount, so he will consider it
-> if you're a skilled gunner and have a tough transport ship like the bison, fight him
-> if you want to troll him, shoot your own cargo when he forces you to drop it (Edit: do this only if he's trolling you/bad-none roleplay)
-> you even can try to hire him as an escort