is phobia. I don't think there is a specific diagnostic name for 恐同症.
Key: irrational and disproportionate fear to any ACTUAL danger.
exposure will cause anxiety.
if his/her social function/behavior changed, then medical help is needed.
Test (repeat this test many times): stay with a 同性恋, if cry or want to cry, freezing, or other anxiety like physiological reaction, then it is a phobia (phobic disorder).