I guess having watched mental illness up close and personal (my mother is bipolar and suffered a pyschotic break as a result 10 years back - on her meds and doing well now), I do not throw the term "mental disorder" around lightly.
My experience with my kids, 2 of who were at very impressionable ages, is that they fear mental illness. That is not what I'd want to instill in them, that gays, as mentally disordered, are to be feared. But that's just me.
We can agree to disagree, but any man that wants to be buggered up his rectum is probably suffering from severe depresssion - a mental disorder.