When Should Schools Refuse to Ban Student Activities?

Here’s a news story that caught my eye. At York University–a university in Toronto, Canada–the student union has decided to ban funding for an anti-abortion group on campus. Read the story here:
York U to Ban Funding for Anti-Abortion Group
This is how it works on many campuses: the student government, or some similar student run body, is responsible for distributing a designated portion of student fees amongst student groups. Usually this goes fairly smoothly.
However, because some campus groups are controversial, sometimes this becomes a big issue. Students, and sometimes community members, argue that students shouldn’t have to pay a portion of their fees to fund groups they disagree with. For example, in a number of U.S. schools, conservative students have protested student fees that fund LGBT groups.
Is this a good idea? I tend to think not, for the most part. As long as a group isn’t doing anything illegal, isn’t abusive to other students, and doesn’t promote rhetoric that is outright hateful, why should they be excluded from student funding? Granted, I don’t know much about the pro-life group in question at York University, and if they were being severely disruptive or engaging in illegal activities, perhaps the decision was just. But if all they were doing was spreading their opinion, albeit in ways that might make others feel uncomfortable, why deny them funding?
Of course, not all students agree with the mission of a group—but so what? You can always start another group, like a campus pro-choice group. Part of the beauty of a college or university campus is the opportunity students have to be exposed to diverse ideas. Thus, a student may disagree with the principles behind a student group–but may agree strongly with the idea that it benefits everyone when all have a voice.
Of course, the problem is, where do you draw the line? Obviously, some groups aren’t going to get funding, like a white supremacist group. But what if in response to an LGBT organization, someone started an anti-gay organization on campus? Personally, this seems to me to be quite different than starting, say, a pro-life group that forms in response to a pro-life group. But is it? Whenever you talk about limiting speech) or funding for speech, in this case), you risk a difficult situation.
For the most part, student groups should be funded equally, no matter what. But obviously there’s a line that does need to drawn somewhere– and I don’t know exactly where I feel this should be. What do you think?