Firstly, the rule of ramming armor into armor is pretty questionable. It should really only be for initiated people, but you guys were already initiated anyway, so it doesn't really matter. If an admin sees this post, please fix the rule. It's really bullshit.
@Quenton, you really can't use the excuse "they saw me coming for them and it's their fault" because it's never their fault for something like that. They had the choice to do whatever you wanted, and you can't blame someone for not doing something you would do. In my mind, it's completely your fault because you decided to ram them and you knew they were behind the hunter. Even if that's true however, since all you did was ram the hunter, and they were hit by it, you should be permitted to finish them while ragdolled, since they were hit by the hunter, not you. In my opinion, this should be unpunished since there is no actual rule on it. The result of this situation will probably provide clarity for this kind of encounter for any future incidents like these, meaning other people probably would be punished if the same thing happened to them afterwards. There is one token of luck you got in this situation though. Had that first guy not gotten into the hunter, and he got hit, that would clearly be VDM. He was already standing there, and you would've hit him before the hunter when he stood his ground. That would be a punishable offense. But hey, that's not actually what happened. Lucky you.
Overall, you were not necessarily in the wrong. There's currently no rule on it, and you got lucky with the driver getting inside. In the future, once this situation is settled by @Olio, if this were to happen again, it most likely not be allowed. This time, however, you're probably going to get away with it. It's a gray area, as if someone else ran them over, then you shot them.