In my opinion neither "RDMed" because player A killed B in self defence and player B failed to kill player A. Therefore Player A's actions were not random, and player B's actions did not lead to the death of player A.
In any case, the standard is 6 innocentA v innocentB,C,D,E,F,G kills before ban or kick is to be mentioned. Therefore, Player A would need to kill 5 more innocents to at least qualify, or player B would need to have killed 6 innocents before he was killed.
But I don't see any fairness in letting you, me or whoever the attacked is to be killed by a player who attacks you for no reason. Maybe he is having fun by doing it, but he is messing with other player's enjoyment of the game. Unless you consider it funny to kill somebody who attacks you and you think "He is T no doubt" and you go and check him, he is Innocent, and even more you lose more karma than him
Also I have another doubt: Are the Rdm kills accumulative? I think they should be because I have seen the following issue happening in game:
ROUND 1:
Player A rdms player B and player C, player B was Innocent and C was Traitor. Nothing happens to him because he rdmed 2 players only.
ROUND 2:
Player A rdms Player B and D, both Innocents. Nothing happens to him because he rdmed 2 players.
ROUND 3:
Player A rdms Player B and D, both T. Nothing happens to him
FINAL ROUND:
Player A rdms Players B,C,D,E,F and nothing happens to him because, as some say "Final round is rdm round"
So in short, some smart people do a lot of rdm in one certain map, but without surpassing the limit of 3 rdms per round.