Re McKinnon:
2) One of her competitors had beaten her on numerous occasions as recently as that week.
It's not unfair only if McKinnon beats every woman in the race - it's just as unfair if McKinnon only beats some of them.
The women who would have come second or third, if a person with all the advantages of biological maleness hadn't been in the race, have every right to feel angry and cheated, as does any woman McKinnon placed ahead of thanks to the advantages of male biology and male puberty, even if it only means that woman is now ranked 20th instead of 19th or something like that. It simply isn't fair.
FWIW I'm pretty sure most transwomen know this perfectly well and wouldn't do this, but it's bad enough that some do and the rules need to be sorted out.
No one is tweaking mens' races so that transmen have a chance of winning races, e.g. by making all the male competitors take peformance-reducing drugs. It's considered good enough that transmen (like most ordinary people) have chances to take part in sport generally, even if there's no event tailored to their unusual physiology (female but with testosterone over the top) that means they can get actual medals.
But womens' races are being opened up for transwomen for precisely that reason - that it's not enough for transwomen to be able to take part in sport generally, they have to have a chance to win something, even if it's unfair on the women they displace.
It's not true talent that's getting them those results - there might be some talent, but there's also a big helping of the advantages of male puberty, male body size and so on. Surely them having the chance specifically to win medals is not so important that they should just be allowed to displace women from women's competitions even though it's clearly unfair.?
They do have alternatives - they can e.g. cycle as a hobby, like most people, or take part in mens' or open competitions for the fun of it and improving their personal bests even though they know they won't be able to win (again, like most of us). They could also campaign for trans categories similar to the paralympics, if they wanted to. Taking medals from women should not be the first choice. (And you can be opposed to that even if you are someone who thinks that transwomen should be treated entirely like women in other contexts.)