I guess he considers her as his sister .. It is versha nly who have forgotten everything being done for her.. She dont even respect her di.. And bout her doing this unintentionally : what if Archana got hurt and lost the baby if it was even unintentional ? It was just spontaneous reaction and moment that he slapped Versha.. One is bound to loose his cool .. After all Manav is a human, or isnt he?