Modern people spend so little time thinking about death that they often are incensed when they hear stories like these. For example, graveyard real estate is at a premium. More people die than can be fit in them. When you die, your corpse lies in the ground for a few years up to a decade at best. Then the gravedigger digs up your remains, put them in the trash and the next corpse is put in the hole. This is why grave digging requires a strong stomach -- it is far from certain that the corpse has fully decomposed. The trash is hopefully incinerated, providing energy for the living. Literally from Dust to Dust.

Same thing with tombstones which are recycled all the time. All larger cemeteries have huge stacks of stones waiting to get crushed into gravel. I cannot say if the practice in Communist countries specifically targeted Jewish cemeteries and if it was therefore antisemitic. Now whether the antisemitic part is not scrubbing the stones clean from inscriptions. Perhaps a large number of Jewish cemeteries were derelict due to the dwindling number of communities and it was easier to take stones from these?