>>8650It is considered an abnormality. You use the word "abnormality" when you very clearly want it to be considered a pathology.
It is not considered a pathology because
it is not pathological, either to the individual, or to civilized society, or indeed to the evolutionary chances of one's broader generic group: there are several patterns (discovered because homosexuality is/was considered abnormal!) that suggest it is, in fact, desirable.
e.g. birth order effect - you're more likely to be gay the more older brothers you have, unless they're adopted - can plausibly be explained by the evolutionary trade-off in balancing "son who reproduces" against "son who provides childcare/protection/labour" etc tipping to the latter the more sons you have.
Remember, evolution works in terms of genes, not individuals.