Has nothing to do with being gay. Relationships tend to be transitional. We are here to play ball not to engage in drama. It is an activity that is detrimental to the success of the team. If it was a coed debate team I would have the same policy.
Of course it has something to do with a high percentage of gay participants. That's why the issue exists.
It isn't like you can have a rule that players can't engage in having relationships.
Beside teammates having relationships with one another, there are other issues. Another common issue is one teammate stealing another teammates girlfriend. It happens. Drama doesn't go away at the college level.