I heard President Trump finally gave in on this issue (depressing), but even his speech on it didn't give actual reasons.
"They'll be outcompeted" isn't an argument when the very institution you're worried about provides no value to society, sucking up cash to produce famous lesbians who hate men. The world definitely needs more of those, said nobody ever.
In my opinion, the argument is framed entirely wrongly. It shouldn't be "save women or you side with trannies", it should be "Repeal Title IX and kill women's sports off for good."
OP's been made aware of this numerous times. He just won't accept the answer.
On the flip side, here's what he sees as a solution:
He makes it seem like repealing Title IX is just one election away from happening.
The truth is, for that to ever happen, you'd have to raise 3 generation of children all across America to undo the brainwashing that their parents/grandparents/great grandparents endured.
Needless to say, his solutions are not going to happen any time soon (if ever).
I think we all wish his solutions were viable, but they're not, at least in the current political climate.
It is, just show spine. All oppressor classes lash out when their power is removed, that can't be avoided.