Online attacking is a part of the game. If one of my fleet member is raiding and online attacking someone with money out, I have no problem with that. Furthermore I encourage it. If someone has left money in the hold, they are painting a target on the side of their ship.
Retaliation attacks are anticipated and so long as they do not become unreasonable are fine. If you online someone steal a couple of 100k and they yard you 3-5 times its still worth the time. If it gets out of hand, let a fleet leader know.
That being said, FDR does not endorse online attacking as a form of harassment. If someone comes to me and tells me a fleet member of mine is harassing them unduly I will put a stop to it. I don't expect to see that kind of behavior out of any members of FDR, as it is not in the spirit of The New Deal.