Dictionary Definition:
1.deviating from what is normal or usual, typically in a way that is undesirable or worrying:
This would indicate that usually there is a pejorative element to the description. Certainly that is the way it has always been used when others have referred to my sexuality. But never to my left handedness. So there is imo an element of judgement when the term is used.
I remember at primary school being told we all had to write with our right hand. Any one caught trying to write left handed, felt the ruler come down on it.
It was considered abnormal then. Something unwanted. Something undesired in a person, being left handed was looked on as a handicap, most things were designed for right handed people.
I take your point though, no one likes to think of themselves as abnormal.
But we still need a model of what's normal and what isn't, it's just left handedness and gay is just being redefined as normal, as in the past it wasn't.
However most people think of "the elephant man" as being abnormal, because that isn't how most people are.
Medical science has to have a model of what is considered normal, to differentiate it from what isn't.
Although it's probably better to describe a condition as abnormal rather than an individual person.
I suppose we all have our ideas on what is normal and what isn't, based on our own experiences.
If someone strikes us as abnormal ( which is often seen though behaviour ), then it makes us uncomfortable.
There are people (not homosexuals) who make me very uncomfortable, and finding them worrying is a good term to use.