People should not be denied participation in sports for which they qualify on the basis of their physical sex, and should be given the right by law to participate on the basis of their gender identity.
"Should not" in the moral sense? I would agree with that. I think it is very wrong to make children, especially, targets for social rejection and violence on the basis of social norms they have no real power to affect.
Politically and legally, I don't think the government should be telling people who can or cannot participate in a sport in the first place, let alone with formal sex discrimination as their sole guide to enforcing said rules. Why would anyone consent to that? If that had always been the law, women would not be allowed to participate in most sports, as they were historically barred from them in almost all cases, and were only able to change those conventions by violating perceptively male spaces (and, once again, sartorial rules).
Do you think that the government should never have passed Title IX at all?
But since you bring it up:
Title IX is one of the most important amendments in the history of the Federal Education Code, and
I support it wholeheartedly. I also routinely advise and inform my students as to their rights under Title IX, and assist them in securing those rights should they need it. Patsy Matsu Mink, who helped rescue the bill when it was being ripped to shreds in the House, is another personal hero of mine.
Title IX explicitly forbids discriminating on the basis of sex, including within the domain of sports,
including every form of exclusion on the basis of sex, such as attempting to expel someone from a program because you believe them to be of the "wrong" sex as you have been advocating for in this thread. It is not in any way a hindrance to gender equality in athletics, on the contrary it created considerably more weight to existing state and federal guidelines requiring equality of opportunity for all students regardless of sex. Quite revolutionary in 1972, and still controversial as we can plainly see.
Are you aware that your TERF buddies are currently trying to have
Title IX eviscerated once again? Some friends! They would have women bullied out of the colleges altogether if they could, but they'll settle for sports teams if that's all they can get.