Allah has prescribed criteria to let us decide what is forbidden and what is allowed in Islam in the matters of morality. Here it goes:

إِنَّمَا حَرَّمَ رَبِّيَ الْفَوَاحِشَ مَا ظَهَرَ مِنْهَا وَمَا بَطَنَ وَالْإِثْمَ وَالْبَغْيَ بِغَيْرِ الْحَقِّ وَأَن تُشْرِكُوا بِاللَّـهِ مَا لَمْ يُنَزِّلْ بِهِ سُلْطَانًا وَأَن تَقُولُوا عَلَى اللَّـهِ مَا لَا تَعْلَمُونَ

Say, “My Lord has only forbidden immoralities – what is apparent of them and what is concealed – and sin, and oppression without right, and that you associate with Allah that for which He has not sent down authority, and that you say about Allah that which you do not know.” (7:33)

Now it is the person involved to decide something is moral or not on the basis of the morally acceptable notions, custom and culture he or she is living in.