YANBU. Definitely.
I agree with people saying YANBU, but if we want to win this argument about sport we have to get familiar with the facts about specific cases. Cricket is an interesting case because the waters have been muddied for a while. I completely agree that making women's cricket effectively mixed sex would massively damage the sport but sex separation is not as clear-cut in cricket as it is in, say, weightlifting,
So the facts are:
1.) Women who play in these type of sports on men's teams put only themselves at risk from injury. Men who play in these types of sports on women's teams put only the women at risk from injury.
2.) Such women compete against players who are physiologically superior to them. I won't list all the ways, but speed and strength are two obvious areas where women are disadvantaged. The difference between the sexes is so pronounced, that these women although elite level in their own sex are only good enough to compete in much lower level leagues in the opposite sex.
Such men compete against players who are physiologically inferior to them. The difference between the sexes is so pronounced that mediocre males can win against elite female athletes.
That's why we have been treated to the sight of an over 50-bloke (ie an age where no man would outperform 25-year-old male elite athletes) in an elite college volleyball team, boys who are slower than the slowest competitors in the boys' races nonetheless dominating the girls' races and so on.
No, cricket hasn't muddied the waters at all. Many sports could and/or have allowed women to play or compete against men. It's just incredibly rare that a woman comes remotely close enough to be competitive against top-or even low-level men.
For example, my friend's son is 15. Gangly legs and knobbly knees and shifted centre of gravity an' all he still runs faster than Laura Muir, the current world champion.
That's what you're looking at: dozens of elite women good enough for mid-level or elite male sports. Many hundreds of thousands of men good enough for elite level female sports. Millions good enough for mid-level female sports.
Not saying millions of males will enter female sports, but where there is money to be had (and there often is these days in elite sports), enough mediocre males will take advantage of these new rules that they will seriously damage female sports.
So, YANBU. These sports organisations who put male desires over and above fairness and the safety of women are being very unreasonable indeed.