Tough situation. Their response doesn't sound crazy to me. You have to cut something if you don't have enough money, and if I had to choose what to prioritize, I guess it would be core science research too.
But, how did they let the budget shortfall get so large? Did this catch them by surprise or something? I'd expect this to have been a slow ramping down of new grants and renewals over years rather than a one time catastrophe.
My post-graduate degree and currently only publication is in a social science area. I'm sympathetic to that kind of research in some ways, but pretty cynical about it in other ways. Shrinking the pool of social science researchers down to a much smaller and more competitive group does not even sound like a bad idea in feast times, let alone in famine.