Grammar homicide can have multiple definitions.
1. grammar homicide is defined as more than one grammar mistake per paragraph.
2. sending a follow-up text where you mistakenly correct grammar, only the correction is actually wrong. And then make a silly comment how you had to correct your grammar b/c it was a cell-phone auto correction.
3. having to spend too much time correcting other peoples grammer.
He committed grammar homicide when he sent that text.
and
I suffered from grammar homicide after spending five minutes reviewing this manuscript.