I think it make sense as it is, by default Caliban are Kill-on-sight, but with proper upbringing and training, the lucky few Caliban with understanding parents or a Morninglordian upbringing can learn to project an image of harmlessness. While no decent Barovian would bother to consort or mingle with such a monster, one might deign to allow him to pick up one's garbage.
(I often compare Barovia to my hometown of Saint Louis as both have declining levels of education, sanitation, and safety; my mother would cross the street to avoid having to walk near a person of another race, but she does not care who drives the weekly garbage truck so long as she does not have to talk to them.)
Let us compare two well known examples of Caliban.
Low Charisma, Low influence Caliban: "Leatherface" from the Texas Chainsaw Massacre
High Charisma, High influence Caliban: "Quasimodo" from the Hunchback of Notre Dame
I think the problem with Caliban player characters is that many players choose stats to maximize dungeoning potential and stat-dump social niceties (or at least I did when I made a Caliban for New Character Week), so when the low-intelligence, low-charisma Caliban shambles into Vallaki wearing rusty, blood-stained plate mail and shaking a battle-axe like a baby-rattle and shouting garbled indecipherable words (you do not annunciate properly if you have an INT lower than 8, I believe), they would rightly provoke a suspicious and deadly reaction from the Garda.
To demonstrate, let us look at the most famous Caliban hero, "Sloth" from the Goonies, a good-aligned yet low-charisma, low-intelligence, low-influence Caliban:
Sloth is a good guy who fights crime, but if that crashed through my window and shouted, "Hey, yuu guyz!" waving his butcher's knife, I would evacuate both my bowels and the premises.
But I suppose if a Caliban quietly limped around the back of a restaurant to ask about employment opportunities, they might be tolerated.
Just tell me that this would not be at least a little bit frightening if you saw it:
[youtube=425,350]http://www.youtube.com/watch?v=U6luYQR20wA[/youtube]
http://youtu.be/U6luYQR20wA//EDIT: fixed broken links