It's the groove. Old Lps have big 'ol grooves. They can be thrashed a lot and still have a lot of fine groove left. (especially if your diamond sits at a different level than the one that trashed the record in the first place... then you basically have a brand new groove in a rotten looking record!)
Later Lps have much smaller, shallower grooves and do not fair as well after being trashed.
Also,
The guy worried about destroying his expensive ($$$$) MC cart has a point! A bad nick can rip that delicate Moving Coil stylus diamond right off. Most MM carts are study enough to handle a hard pull from a gash in the LP (I am sort of making this up, so if your experience is different, please go ahead and diss' me plenty!)
Later Lps have much smaller, shallower grooves and do not fair as well after being trashed.
Also,
The guy worried about destroying his expensive ($$$$) MC cart has a point! A bad nick can rip that delicate Moving Coil stylus diamond right off. Most MM carts are study enough to handle a hard pull from a gash in the LP (I am sort of making this up, so if your experience is different, please go ahead and diss' me plenty!)

