Lets look at this a different way with a hypothetical.
Lets say a group of protesters is against a farmer harvesting tomatoes for whatever reason. The protesters trespass, they try to interfere with harvesting, they even go so far as to vandalize the farmers combines.
Now, does the farmer now have the right to run over this group of protesters with his pickup truck?
If you don't believe the whaling ship made a hard turn to starboard to ram the batboat, then there is no point in discussing. Because with this belief, then of course the whalers are not at fault for anything, the batboat purposely 'jumped' in front of them.
I don't see it that way. To me it appears the batboat was placing itself close, then the whaler purposely turned starboard to facilitate a ram. While the batboat 'greenies' are undoubtedly guilty of all sorts of maritime violations, including using speedboats to violate the 'spirit' of maritime rights of way, the whalers are guilty of using their vessel in a purposeful act of deadly force.
Let's make your hypothetical scenario more believable, Dredger.
Let's say this group of tomato harvest protesters trespass, try to interfere with harvesting, and as you said, even go so far as to vandalize the farmer's harvesting equipment.
For a more like comparison, and because you went way too extreme with your scenario......let's say the farmer is in his TRUCK that he hauls his harvest to the market with, say a GMC 6500 series for fun, and while he is on the way out of his field, the protesters have entered onto his land again and are harassing him, pacing him in......a 2006 VW Beetle.
They get up beside him, pull a little ahead, then suddenly cut in front of him, maybe just a swerve to test his nerve, then pull ahead far enough to stop and turn sideways, partially blocking his path ahead.
You now have a 25,000 pound truck traveling at whatever speed, let's say it's 30 miles per hour, and the Beetle, all 2900 pounds of it, is stopped only 30 yards ahead. The farmer tries his best to slow or stop his truck in the distance allowed, and at the last minute swerves to the left and hits the left front fender of the Beetle, smashing it in.
Who is to blame? Who is at fault?
The hypothetical comparison you left us with isn't even applicable, mainly because you are talking about an incident that occurred in international waters and trying to compare it to one taking place on private property.
Sadly, some parts of the country would take the side of the tomato protesters. Private property seems to be an evil thing anymore, and the rights of said owners are secondary to those who subscribe to the belief that "what's yours is mine".........thank God I live in a place where common sense would prevail even in the hypothetical scenarios you and I laid out.
First the sheriff would be notified, trespass warnings issued, and after the regrettable incident, caused by the tomato harvesters themselves, transpired, not only would they have a smashed vehicle, they would be spending time behind bars (at least in the part of the country where I live).
After watching just about every link to the videos regarding this incident, the only conclusion I've come to is that the protesters, despite all the donations and nice toys they've received to fight this little "war" of theirs, are idiots. They take a much more nimble craft and place it in close proximity to a much larger vessel, practically in it's path, and try to convince the world that they were intentionally rammed.
Even a landlubber such as myself knows that a ship the size of the Japanese vessel takes forever to stop, and responds slowly to rudder commands.....even in the video posted on their own website, one can see the smaller boat easing forward into the path of the oncoming reseach/whaling ship. The "hard starboard" turn could just easily be the ship hitting a swell......the attempt to turn to port and not overrun the smaller boat directly (and strike it right where the crew was) is crystal clear.
My opinion is that a) the Japanese vessel is in international waters and not violating any of the treaties; 2) the protesters, despite all their funding and donations, look like fools, not possessing the basic seasmanship skills needed to conduct their protest in a manner that anyone but the weakminded would take seriously; and 3) eventually, probably sooner than later, someone affiliated with the protesters, is gonna get killed, "thrown under the bus" as it were, sacrificed in an effort to make more headlines.
The fault for the incident, in my opinion, lies clearly with the "captain" of the Adi Gill, or whatever the boat was called. He placed his smaller, more nimble vessel, in harm's way, and could have easily moved his craft out of danger. He chose not to........all a part of the propaganda program you will find on the protesters' own website.