From my perspective, I can't totally speak to this as it is written. First, I don't believe in "sin" in the conventional Christian sense. I don't see most things as black and white, right and wrong. Rather, I ask- what is the best possible choice?
There are situations in which none of the options is sinful (in the Christian way of thinking about it), but there is a clearly best, most harmonious choice that is most conducive to spiritual development. Conversely, there are actions considered by monotheist traditions to be sin that I think aren't sins at all.
All that said, love is trickier than it seems. Real love stems from a sense of connection to and service in the Divine, the liberation of thought and emotion this produces, and wisdom of knowing oneself and others. Only when we are really connected to the greater whole, the Mystery of which we are all a part, and only when we are free from our egoic assumptions/needs/identities/etc. can we be free to understand ourselves and others for what they are... to really know them. The deepest, most real kind of love is borne out of this knowing, this wisdom of understanding ourselves and other beings.
When we love in this way, then our actions inherently are in service to the Divine and we are able to be harmonious with all-else-that-is. And so, in that wholeness, there is no sin.
But...
My general feeling is that this takes dedication and cultivation at a level few humans seem to be willing to engage. And thus, what most people think of as love isn't love at all. It's a grasping, needy, selfish feeling... it's the desire to shore up our egoic identity through forging bonds of solidarity with some and use this to dismiss others. It's self-serving and disconnected from harmony.
So it isn't surprising that there is also, then, a preoccupation with sin in the sense of categories of right and wrong actions. We can feel good about ourselves without much critical self-reflection or commitment to transformation through adhering to rote categories of actions we should and should not do. This is in opposition to the process of actually learning who we are, becoming self-aware, and choosing to tackle the vast world of "grey" through cultivating our capacity to be spiritually connected, dedicated to serving others, and setting our sights on what is *best* (not what is *right*).
People do horrific things all the time, believing they are doing it out of love. Learning to really love is difficult.
