Biden's position will win him the votes of people who think common sense is a good thing to have. Every defense of trans athletes (code for trans women competing as women, a generalization that gives away the rhetorical game) must explain why sports are segregated by sex in the first place. If you can give a coherent defense of that practice, then you go on to explain why someone born with male chemistry should nevertheless be allowed to compete as a woman. If you want to attack the division of sports by sex, have at it. See how many votes that gets.