You might want to reserve the use of the word "fallacy" for cases where an argument's logic does not follow. Ironically, use the word otherwise often betrays one's own cognitive biases.
As far as my endorsement, I don't think I could state my position any more clearly than I already have: "...maybe we should reconsider the wisdom in granting some small portion of our freedom to every other voter. 42% of Americans believe in ghosts..."
You have yet to make an argument that "representatives are theoretically there to guard against majority tyranny." If you had, it wouldn't be a just world fallacy.
Correct, I have no interest in arguing that position. Any highschool graduate should immediately recognize "majority tyranny" and the political theory that it is connected to. If I had argued the virtue of representative democracy, it might have been biased by the just world fallacy, but I haven't - so it wasn't.
"Theoretically", we had kings because of the divine right of kings. Theoretically the American expansion was justified by manifest destiny. Theoretically women were not allowed to vote because "90% did not want it" or because it would "place the government under petticoat rule".
Theoretically, today, we have representatives in government because the people aren't smart enough to represent themselves.
Every system of power and domination creates a justification for its own existence and it's nearly always bullshit.