I am aware of the importance of the concepts of pederasty, androgynity and the 'lesbos' in Greek culture, but I wanted to know if the actual concept of love was considered universal or pansexual, and if individuals could openly love people of the same-sex without suffering prejudice.
Ancient Greece is a term that refers to at least a couple hundred years and some significantly different peoples, some of which we don't have very accurate accounts of, so any generalization like this has to be taken with a grain of salt.
Concerning golden age Athens, which is where most of our sources come from, I wouldn't say the concept of love is not precisely gender-free. Perhaps a more cynical explanation would be that Athenian (and a lot of ancient Greek culture in general) was highly misogynistic, so there was a certain suppression of the value of male-female relationships. In aristocratic families, women lived separately from men, they celebrated separate holidays, they didn't eat together, and generally a couple was not expected to spend much time together outside of sex (for which also the man could seek outside partners - slaves, concubines, prostitutes). Men were not viewed positively for spending time with their spouses and women were not expected to share their opinions or thoughts with their husbands. For aristocratic couples, women married at around 13 while men first married in their mid-20s, so while sexual attraction was an important component for marriage, clearly mutual understanding was less valuable.
Pederasty provides an interesting case, because there is an age element to it. It was sort of meant to be a phase that the younger boy (eromenos - the beloved) grew out of once he started growing a beard after which point he would take on the role of a senior partner (erastes - the lover) in a new relationship. Couples that continued this relationship past the younger lover's coming of age were generally mocked and despised.
To add one further element of complexity, our culture holds romantic relationships to generally be the most important in an individual's life. Greek culture places a much higher value on friendship as the highest/most important relationship in a man's life. The Greeks actually distinguished this in their speech where eros and its cognates mean sexual love while agape and its cognates mean love in terms of affection which occasionally slides into the sexual register, but doesn't necessarily have any sexual coloring.