I've actually seen a good number of people from the LGBT community say they've been to events at BYU without any problem. That isn't the issue.
The issue is LGBT students attending BYU, but wanting to actively live the LGBT lifestyle. There's definitely a distinction here. I think this is BYU's biggest point. Anyone is welcome on campus, but in order to be an enrolled student, there are certain expectations (it's a private university after all).
Also, I don't think you can make any half-way changes to the HC, like drawing the line at "sensual displays of affection." Either BYU stands their ground (which we all know they will), or they remove that entire section from the HC, allowing homosexuality on campus.