Because the Left are in power, their ideology is mainstream and so they choose the ground of debate.
The provides a very powerful advantage, which is that while the reality is that they are using the Global Bureaucracy coercively to implement totalitarian Leftism; they can present their policies idealistically, as if occupying the moral high ground.
To argue from Christian premises is impossible, because the assumptions are not shared. This means that Christians often get manoeuvred into arguing against Leftist policies on grounds of expediency, on the grounds that the policy is ineffective, counter productive - on the grounds such that the policy will reduce wealth or increase poverty; reduce freedom or increase tyranny; will impair happiness or increase human suffering.
But when Christians argue for the Christian perspective using mainstream secular criteria of 'bad consequences'; this mode of argument itself has bad consequences.
For instance, Same Sex Marriage was proposed by the Left on
idealistic grounds, but usually opposed by Christians on the grounds that it was
inexpedient... that SSM would lead to bad outcomes for children and for
By bad outcomes - the Christians, here, meant that SSM would have adverse psychological and physical consequences of children; that children would ('on average', probably...) suffer impairments to their happiness and health.
Although the arguments were correct; these are the utilitarian arguments of a social policy analyst - not Christian arguments! Hence they were counterproductive - as well as ineffective.
Or 'Traditional' marriage was defended by
Christians as an Institution, not just a personal decision.
That the Institution was built-into society - with implications for law. That we needed the marriage Institution in order to prevent worse outcomes... But the cultural context is that all Institutions - including marriage - have deep, intractable, problems of
We we live in a world in which institutional authority has
been crumbling for several generations. So defending marriage as an institution, is to defend marriage as part of a world-view that has been crumbling with increasing rapidity since the middle 1960s.
Unsurprisingly, the Institution argument was ineffective. But worse - it reinforced an idea that the individual's judgment, and his essential life, should be subordinated to external 'social requirements'... a deeply anti-Christian perspective.
By contrast; in secular society and within
Christian churches; the sexual revolution agenda is proposed on
idealistic grounds! Proposed as A Good Thing in and of itself - because SSM is more-Equal, and Equality is Good.
'Good' as such, and whatever the outcome...
In effect, the advocates say that SSM is a good thing, and damn the consequences! They don't 'argue', but instead they state that 'we' ought to introduce SSM because it is Good; because it is (supposedly) More Christian (because 'Love'...) - and without regard for 'what happens next'.
So the anti-Christian radicals have claimed the higher moral ground; and the real Christians have - by arguing on the secular ground - undermined their own moral authority.
And what the average person sees here is Leftists being idealistic and moral; while Christians are arguing that there will be bad materialist consequences.
So what should real Christians do? More exactly - since we do not get to choose the context - what can we do, and what can't we do?
Well, Christians cannot argue.
Christians can only - like the Leftists - state our convictions.
So, the opposition to SSM would need to be stated in terms of the positive, Christian convictions that SSM violates. In a form such as 'We believe XYZ, therefore oppose SSM'.
If there is going to be any 'argument' it will need to be about XYZ - which is about fundamental assumptions, which is a metaphysical discussion - and any such discourse ought to benefit Christians, since mainstream modern Leftism denies the reality of metaphysics; and denies that there are fundamental assumptions that need to be chosen.
Any discussion that shows that mainstream materialist Leftism is itself based on assumptions, is a plus.
So, Christians must stop acting like pragmatists or social scientists; and start revealing their idealism... Must stop arguing, and start stating their convictions.