There have been hundreds of women who have spoken up and talked about the impacts on women's rights, why didn't he use their words?
He very, very often does. That thread is excellent, nothing wrong with highlighting it.
Are male transpeople opinions more valid
I think it's fairly obvious he doesn't think that.
or have a bigger impact?
Sometimes yes, because they show up the lie that the only people concerned over self ID are transphobes. As Kristina rightly points out in the thread- she gets away with saying things that women are shouted down for.
The people to people to blame for women being shouted down are the ones doing the shouting (squints eyes at LOJ, Penny Mordaunt, stonewall et al).