The best advice that you can give your friend is
1. Never ever fly without covering the rebuy costs.
2. Always be aware of who's in your instance & what they are up to. If any player makes any move towards your ship then you either fight or flee.
A player ramming your ship is a sign that's not good & needs to be acted upon. I certainly wouldn't have been around for the second or third ramming to occur.
^^^^ this. Why did he stay for repeated ramming?