the outsized symbolism she represents...they could have chosen almost anyone else for that ceremony with zero public involvement in an obviously heated environment...but they chose to ignore the students and faculty request...so they did their symbolic duty and walked out.
The students and faculty are keenly aware that abortions will be driven underground in states that ban them, resulting in great harm to women who won't have good, professional medical care
...especially those without means to travel, etc. those Doctors and Students are standing up for the women who are being ignored by such as Dr. Collier.