The difference is that economic conservatives are not always wrong and social conservatives are not always evil.
IMO and IME, economic conservatives sometimes have arguments worth listening to. But their actual, unstated motive is usually if not always to defend the interests of the haves, and that is the general tendency of their arguments whether intentional or not – in short, always evil.
Social conservatives, OTOH, while they might well be sincerely well-intentioned Christians or whatever, are always entirely wrong – not about everything, perhaps, but definitely about everything that distinguishes them from others, everything on their particular agenda.
N.B., however, there is an important corollary to that:
In politics, social issues are usually (not always) much less important than economic issues.
E.g., in America we have a lot of needless deaths by gunshot every year. But, in the general scheme of things, that is no more than a bit of oh-too-bad; it is no existential threat to American society, and unemployment blights far, far more lives than does violence armed or unarmed. The Dems (and for that matter the Pubs) should be placing much higher priority on reducing unemployment than on gun control/gun rights.
By the same token, it’s too bad gays are having such a hard time getting SSM recognized; but, they can thrive without it. What matters more than anything else is that the law no longer criminalizes sodomy, etc.
Of course, some pols (in both parties, but Pubs mainly) who understand the above perfectly are not above using social issues as a distraction or a voter-turnout spur.