I certainly think there would be much more of an outcry if trans men were winning against men.
So do I. It's already started in a way. Whereas transwomen are allowed into women's changing rooms, lavatories etc, I'm pretty sure that transmen aren't extended the same courtesies in gyms etc.
And granny - I hate sport too. I think it's as boring as hell. If it were up to me it would certainly never be on TV taking up valuable airtime when I could be watching Miss Marple. But other people do enjoy it, and as I am not a goady twonk like some people I graciously allow them their simple pleasure.
However, I don't want to see any woman unfairly disadvantaged.
And if you really are a "granny", I wonder how happy you would bee if your six year old grandchild was competing against fifteen year olds and beaten in every sport - after all, the bigger, older kids would be deserving of the victory because they are bigger, stronger, faster etc.
Transwomen are disadvantaging those who are born female. And this is even to the extent of skewing violent crime figures. (Transwomen are disproportionately represented among violent offenders, but aren't differentiated in the overall figures.)
You may not care if your female grandchildren are crushed by patriarchy, but I bloody do!