“As God has renounced himself out of love, so we, out of love, should renounce God; for if we do not sacrifice God to love, we sacrifice love to God, and in spite of the predicate of love, we have the God – the evil being – of religious fanaticism.”
-- Ludwig Feuerbach from The Essence of Christianity
This is the beginning of the emptying of the concept of love. Feuerbach had a huge impact on Marx, but also on secular humanism and on certain strains of theology and religion.
I can understand why Feuerbach and others might think this in necessary and a good thing, but I feel that it is short sighted. Doing this can make ecumenical work easier and it would seem to work well at trying to unite humanity. However, it makes both God and love simple and superficial. Whether you sacrifice God and keep only love, or empty God of everything but love, you are making the thing that sits at the center of your existence, your world, simple and superficial. This is binary thinking that insists that when two things are not totally compatible, one must be given up, allowing for the other to take up the space previously occupied by the two. This is simplistic thinking and leads to simplistic ideas, and on this level to simplistic ideals.
'The evil being of religious fanaticism' is of course a problem. But it comes from the simplification of God as well. A fanaticism that hates is the exact opposite of a God that is only love or love without a God: it is a simplification and superficiality in the other direction. It is a God that does not like complexity and any sort of incompatibility and reacts by hating whatever introduces complexity and incompatibility. The reality of God and of love lie in the complexity of them, in the multiplicity, juxtapositions and even contradictions of the ways that those ideas are thought, expressed and felt together in tradition, art, theology, history, etc.
The self-renunciation referred to here is almost without a doubt the crucifixion. Reducing the Judeo-Christian God to that one event is a gross simplification. Reducing that event to one meaning makes it even worse. The story, the history, the theology and the tradition behind the crucifixion and the Judeo-Christian as a whole God is far more complex and deep than that, with layers of meaning and interpretation. These allow for new experience and interpretation of both the idea of God and of love.
Just as the existence of faith necessitates at least the possibility, and usually the occasional existence, of doubt, the existence of something as powerful as love or God, something that occupies the center of your world, requires complexity and depth to be real; it requires complexity to mean anything when it finds itself in the real world. The complex histories, traditions, theology and struggles of the major world religions are a testament to this. Religion (or anything really) needs to be dynamic to be relevant in the world, which itself is very complex and dynamic.
Stripping God of everything but love makes God a simpleton, a caricature of what God has to be to be real and relate to the real world. Placing love at the center of a world without a tradition of thought, stories or art to help define it is one step away from leaving that center empty. Neither are practical, but both are currently very popular. I can't help but think that has more than a little to do with the futility and animosity that fills our public discourse.
A (more modern) philosophical aside:
It is interesting for me to compare what this simplification does to God and love to what Heidegger says technology does to truth.
"The threat to man does not come in the first instance from the potentially lethal machines and apparatus of technology. The actual threat has already afflicted man in his essence. The rule of enframing [a strict and seemingly permanent ordering of things] threatens man with the possibility that it could be denied him to enter into a more original revealing and hence to experience the call of a more primal truth."
-- Martin Heidegger from The Question Concerning Technology.
This can be applied to the idea of simplification of God and love like this:
The threat of religion does not come from a God that is not left behind in favor of pure love and the fanaticism that may come from that. The real threat has already taken hold because man looks to religion for a simple, universal and eternal answer to the question of the meaning of life. This insistence that the meaning of life, or just the rule that we must live life by, must be simple and at the same time applicable at all times and in all places, keeps us from encountering reality and our own experiences as they are and learning from them and acting from a closer relation to and more intimate understanding of them. That the rule is simple and universal keeps us from reality, which is ever changing, in a twofold sense: first, it keeps us from seeing the world directly without the simple and universal filter shaping it and the filter, being eternal and universal as well as simple, cannot accommodate or adapt to those changes; second, it keeps us from responding to the world as it is and limits what we can imagine as possible responses based on the simplicity of the rule that cannot accommodate the complexity and every changing nature of the world. In other words, we cannot experience what we encounter, nor can we react to it, in a close and original way because the simple and universal filter gets in the way.