But the flaw remains that there is no way to prove what the union is. At any given time the honest chain has all the transactions from the attackers chain plus censored transactions, but then the attackers chain releases a new block with more new transactions. How do we prove which was first? That is the entire point of a longest chain rule is we have no way to prove relative order otherwise. This is what I wrote several posts before. You will just chase your tail in circles. It violates CAP.
First doesn't matter. Cumulative POW matters - if the attacker extends his chain by another block, thereby increasing his weight, if he is still censoring transactions, the minority can easily extend their own chain by including all the transactions he has, plus the ones he leaves out?