Well it's unclear. We can make predictions about what the court would do but until the case is actually decided we don't know.

One of the interesting things about the court system that a lot of people don't know is that the whole opinion doesn't count as precedent, so the doctrine of stare decisis isn't nearly as helpful in determining what the court will do in a particular circumstance. There are several parts to an opinion: it is only the holding and judgement which is definitively has the status of precedent. The ratio decidendi (legal rationale) is also precedent, but its status is obscured by the presence of the obiter dicta (things said in passing). It is often up for debate which parts of the opinion count as ratio and which are dicta.

With all that as a preface, I would say that there is no reason why the interests of a high school in restricting the speech of an 18 year old should be treated so totally differently than the interests of a college in restricting the speech of an 18 year old. The age of the parties doesn't appear (to me) to be part of the ratio for the school speech cases.

In Hazelwood, the court held that school-sponsored activities are not subject to 1A protections because the school had a reasonable fear that such speech could be construed as having the school's imprimatur; they therefore had a compelling interest in regulating it that outweighed the 1A rights of the speaker. Likewise, in Morse (the Bong Hits 4 Jesus case), the court seemed to hold that schools can limit speech that was at counter-purpose to the purpose of the school--since one of the high school's purposes was to keep kids off drugs, they had a compelling interest in limiting pro-drug speech that outweighed the 1A rights of the speaker.

From that starting point, I see it as perfectly reasonable that a speech from a meeting of students in a university-recognized organization (SAE) could be reasonably construed as having the university's imprimatur and therefore be limitable consistent with the 1A. Moreover, since the educational mission of the university relies on diversity and tolerance, the university has an overriding interest in not allowing speech that would seriously undermine that mission. Therefore, there is no undue burden placed on the 1A rights of the speaker, and the action of the university is consistent with the 1A.

But I think that the legal argument actually misses out on the better discussion that we should be having, which is what is the point of free speech? Surely, free speech is not simply the protection of sound-waves but the protection of sound-waves for a purpose--the promotion of useful discourse in Politics, Science, Arts, etc. Is there any way to conceive of the type of speech that was occurring with these people as furthering the goals of free speech in the broad sense? If yes, then by all means let's protect it. But if no, who cares about the legal quibbling: for every legal argument there is an equal and opposite one (q.v. Karl Llewellyn "Dueling Canons" 1950). The more interesting arguments are policy arguments about social utility, not mindless kowtowing to so-called "rights".