It was during the gay marriage debate, so the liberal schools' normal hate of a religious school got put on steroids. They were looking to send a message.
Then, when they started to get called out on the bigotry and hypocriticism of excluding others based on "inclusive" values, they changed the reason.
But they couldn't find a legit reason like history of winning, national brand, fan following, venue size, viewership or anything else.
So they made up this lame-butt excuse about their sports conference really being about research.