Are expressions such as "I'll curse his mother's religion" and "I'll curse his parents' dead" considered blasphemy against religion?

This statement is serious, and if its utterer intends thereby to revile the religion, then he commits an act of disbelief (kufr). However, if he does not intend to demean the religion but rather to demean the addressed person, then he does not commit an act of disbelief but merely a grave sin (fisq). Religion is Allah's religion, and it is not befitting to direct evil towards the deceased. A Muslim must guard his tongue except for good and control himself when angry.