Here's the decision itself.
The issue involves a student group called Badger Catholic, at the University of Wisconsin. The University refused to fund activities that constituted worship, proselytizing, and religious instruction.
On the one hand, you could see this as discriminating against a religious group, since other groups are allowed to hold counseling and educational sessions and try to convince others of the correctness of their views.
On the other hand, if the group were to be funded, you could see this as tax dollars being used to promote a particular religion. If I'm a Muslim taxpayer in Wisconsin, I'm wondering why the state of Wisconsin is paying someone to try to convert me.
For myself, I think the question is whether religious activity is special and different or not. If you want to say that the Sierra Club or the Federalist Society are in a sense praying and proselytizing and you should be able to do the same, I think you are right in a way, but then I want to know why the National Organization for Women can't discriminate based on gender but the Lutheran Church can. Why do priests get to write off the cost of their housing when the executive director the Yoga Society doesn't? What do you think?