Secular humanism is the standard modern belief system, supposedly derived from science and the ideals of the French Revolution but actually a sort of perversion of Christian ideals which has taken a part of the truth and puffed it up out of all proportion in the context of the whole, at the same time neglecting, if not categorically denying, other more important parts. But whatever its initial inspiration, it is now clearly driven by forces seeking to separate Man more and more from God, to lead him to deny his source and restrict himself to the material world. For the last few decades one of the key ways these forces have been doing this is by attempting to deconstruct the human form in terms of its fundamental identity as two distinct and complementary sexes. Once this reality is lost the human being is disconnected from spiritual truth and its nature can be reassembled from below. If this sounds a little excessive to you that merely shows how far the process has already gone. Previous generations, or maybe even you a few years ago, would not have thought so.
Truth can be represented by a cross with a vertical and a horizontal axis and it should never be forgotten that the latter hangs on the former. But this is precisely what secular humanism does forget (or deliberately ignore), treating the horizontal axis is if it were all there is. However when you expand your parameters beyond the second commandment to include the first you see that loving God necessarily demands loving truth, and that means that you are obliged to condemn falsehood where you see it and not simply support your neighbour in his acts and beliefs regardless of what they are. The humanist way, which is relativistic, thinks that loving your neighbour means accepting him whatever he does or thinks as long as it doesn’t cause obvious harm to others but this can easily amount to the denial of God and absolute truth. This is not love but sentimentality and moral relativism.
For the injunction to love the sinner does not mean that you don’t recognize his sin as sin or that he is a sinner. You cannot use the theory of love to deny the reality of objective truth, and if you do you will have neither for love, real love, always goes hand in hand with truth. True love does not forbear to point out right from wrong. After all, what is the greater love, to encourage someone happily walking towards the edge of a cliff or to pull him back?
When it comes down to it secular humanism can only end in one thing and that is nihilism. You might not think so at the moment because people are often better than the belief system they espouse since God is within us whether we acknowledge him or not. But the more the West uses up its moral inheritance from Christianity, and the further its morals come from their true source, the more nihilistic it will become until its morality will be just a matter of utilitarianism. Secular humanism cannot stretch us or help us grow out of our limited self-enclosed state. It cannot encourage the God within to come out for it does not acknowledge him. The only way it can go is down.
N.B. Many people dislike the word 'sin' because it implies unworthiness, condemnation and all sorts of negative things. But the reality is that it is a perfectly good word to describe that which separates the human being from its Maker and its proper spiritual destiny, and that's a serious matter.