To use a mental health term as an insult against those with whom one disagrees is prejudicial, intolerant and, in my view, totally unacceptable.
To use a medical or quasi-medical term as a form of abuse is not only demeaning to the person being abused, it is also demeaning to those who live with the medical condition.
A phobia is an irrational fear. People who are phobic have a serious psychological problem, and in extreme cases a psychiatric problem. A true phobia is always debilitating and often disabling.
I see no difference between calling a person with whom I disagree a spastic or a mongol and calling him a phobic.
So why do people, especially those on the politically correct left, insist on using the prejudicial term homophobic as a term of abuse against those who disagree with their views on same sex relationships?