I personally feel that there is a big difference between someone calling themselves “Rabbi” and others calling him a “Rabbi”. It is certainly generous and respectful to call a Rebby in yeshiva or anyone revered for good middos with the title “Rabbi” even if he has not earned semicha. However, for that person to call himself a “Rabbi” is simply a sheker and gnaivas daas.
By the way, after shelling out tens of thousands of dollars in tuition I find it troubling that Yeshivos don’t hire people who spent the time, effort and commitment for semicha to teach our children.