CBS
According to Steve Jones of The Courier-Journal (via SI.com), rather than allow the men to support their own school as well as support women's athletics, the NCAA called the trip "an improper benefit."
The NCAA did finally relent and reversed their own decision at some point today, according to Brett McMurphy of ESPN.com. However, by that point, Louisville had already made travel plans to return home.
Most of these decisions by the NCAA are not made because the overbearing organization thinks they are all that bad. Rather, the NCAA is always worried about what the next player or team will want and is worried about setting a dangerous precedent.
Unfortunately for players like those on the Louisville basketball team, the NCAA thinks it is just easier to say "no" to everybody.