There is going to be blowback either way. If they change the rules and force transgender athletes to compete based on the sex they were born with there will be blowback. If they allow transgender athletes to compete as they wish, there will be blowback from women/girls who claim it's not fair or men who complain that they don't want compete against athletes who were born as women.
The interests of transgendered athletes are just as important as the interest of other athletes, if not more because they are dealing with more than just winning or losing.
When it comes to women's sports the majority of those who win are cis women, despite competing against transgendered athletes. Transgendered athletes arent winning medals in the Olympics.
Maybe, it is only the start. Maybe more transgender athletes will start winning and the idea of that makes people uncomfortable.
There are faux worries that female athletes are going to suffer injuries at the hands of transgendered athletes, or that transgendered athletes will suffer competing against cis men. That hasn't happened. There are rules in place to greatly limit the possibilities of that.
There seems to be alot of fearmongering and transphobia poorly disguised as legitimate concerns. There seems to be a misconception or a confusion between sex and gender. Just because a transgender person was born with a penis at birth, does not mean their gender was also many. Transgender people are born with the opposite gender, but often don't discover this till later, and then change their sex to match their gender. They are not simply choosing to change from man to woman or woman to man.
This an in issue being made overly complex because of a few transgender athletes started winning.