The "Rome will become the Seat of the Anti-Christ" comment was apparently not in the original secret written down by Melanie.
http://www.sspxasia.com/Newsletters/2003/Jul-Dec/Secret_of_La_Salette.htm
I skimmed the link and did not see what you are alluding to.
Don't know how you could miss it. Simply read the translations of the children's writings in the above link, and you will not find that comment about Rome being or becoming the " Seat of the Anti-Christ".
What makes SSPX the authority on La Salette?
Matthew 18:6
But he that shall scandalize one of these little ones that believe in me, it were better for him that a millstone should be hanged about his neck, and that he should be drowned in the depth of the sea.
For decades, notwithstanding the fact that there have been false suits against the Church as a means to get rich, Rome and the Conciliar popes have protected child predator clerics at the expense of children. fαɢɢօtry, pedophilia and, reportedly, Satanism, is deep in the halls of the Vatican. Look at the statue in the Paul VI Audience Hall. How can anyone not see the diabolical undertones in that thing? In ways, Rome is the Seat of the anti-Christ right now.
The denial of "Rome will become the Seat of the anti-Christ" by the (Conciliar) Church is no different than the Vatican, today, refusing to disclose the real 3rd Secret of Fatima while sticking with their bogus "secret" that was revealed back in 2000. Huge cover up.