Q: "Why saidin, why not saidar, was tainted?
RJ: Because there were only men in the party that made up the party that made up the Strike at Shayol Ghul, that were setting the seals. In the act of setting the seals, there was a backblast that affected the people doing this. As I pointed out in something…I wrote a piece called The Strike at Shayol Ghul…there was a great division at the time – I don’t know if all of you have read it…or have none of you read it?"
Qs: "Yes, yes."
RJ: "Okay, then you know about the political struggles that were going on, and the different plans to try and end the War of the Shadow, and seal up the….and why various groups thought that one plan or the other was the best way to go. And in the end, what resulted was the so-called “Fatal Covenant” [It was actually the “Fateful Concord” – Terez], which had the female Aes Sedai swearing not to go along with Lews Therin’s plan, that they would not support it. The result of this was that Lews Therin carried out his plan with only male Aes Sedai, so there were only male Aes Sedai channeling there, which was a lucky thing, because if there’d been women as well, then both saidin and saidar would have been tainted. And his plan worked, except for that one side effect of the backblast which tainted saidin and caused him and the men there with him to go mad there and then, and other male Aes Sedai to go mad slowly as they touched the Source and began to absorb bits of the taint. But that’s why saidar was not tainted, because there were only men there channeling during this act of sealing up the Dark One’s prison."

He obviously treats SaSG as canon here, and I think it wouldn't make much sense to write this piece to explain the readers what happened then (apparently RJ couldn't put all the info into the series that well), but that this explanation is actually wrong. But as said, while it isn't explicitely stated, I think it's possible that ta'veren or the influence of the Pattern was also a reason, why the women refused to help LTT, besides the political quarrels.