which is the appropriate source to answer questions like normality of homosexualism, abortion, etc ?

Question

Is it philosophy, science and medicine, sociology, religionor something else?

Answer 1

Politics site provides far more answers than others.
Homosexualists are, to my mind, a genetic mutation held by Nature in reserve in case the planet needs a population decline to save itself if a famine arrives.

Answer 2

Each could and perhaps should have an input, except perhaps religion and philosophy. Science and medicine will tell you the facts of how often it occurs, if it occurs in other species and if there is a genetic background. Sociology will tell you about how various cultures handle it and what the different views are.

Philosophy may have a lot to say but unless you subscribe to that philosophy, it may have little information that the first 3 didn't provide. Religion will make moral judgments on whether it is right or not but most likely will not have a good sense of its normality.

If you're looking for answers about the morality of something, then Ethics as a Philosophy (i.e. the study of moral systems) is a good starting point. Religion will generally express a single given moral system.