His/Her specific ability to engage in combat sports is not something mitigated by transition, that's just science. The scaffolding remains and it's an advantage who's existence is why many sports are gender segregated.
Men, what you do if a he/she confronted your girlfriend, wanted to fight her, and felt justified to do so because of he/she is a women now.
What would you do if he/she started hitting your girlfriend? I don't know about you, but if I ever saw that happening. Then I would be busting out the metal hammer.
And obviously that makes me transphobic....I assume.