I don't think the sheriff will get very far with this stance, as it is the duty of the sheriff to enforce the orders of the court, including orders evicting tenant. Some lender will probably file a mandamus or other proceeding to compel the sheriff to do his duty.
That said, I am sympathetic to tenants in this situation. Often, the first notice tenants have that their rental has been foreclosed is when they are served with an eviction lawsuit by whoever purchased the property at the foreclosure sale (usually the lender). There are many good tenants who get evicted in this way through no fault of their own, because the lenders do not want to take the trouble to sort the good tenants from the bad ones or to be in the landlord business at all. Rather, they just want to unload the property ASAP, which is easier to do if it's vacant.
This communist has no concept of private property, does he?
That said, a typical foreclosing bank will continue to rent to a tenant, at least for a little while.
Many of the occupants that the Sheriff refuses to evict are the delinquent borrowers, not tenants. In fact, tenants are probably protected by a thirty-day notice requirement or the like... just as when a landlord wants possession of a rental property for whatever reason. They do deserve a fair notice period to enable them to move. The borrowers who just won’t move out, though... no sympathy at all for them.