If you know what a vaccine is and think it works, you don't need to care if anyone else is vaccinated. Nobody goes on a tear saying folks who don't use seatbelts or bike helmets need to be rounded up and shot.
Vaccine enthusiasts clearly don't think vaccines work, or, often, don't even know what a vaccine even is.
A needle violates the sanctity of the body, and they feel tremendous envy for anyone who refuses to be profaned. They don't care about the medicine (alleged or real), they only care that if they have to do it (or feel like they have to do it) then you must also have to do it.
Because vaccine enthusiasts clearly don't think vaccines work individually, they also don't think they work collectively. It's almost purely an expression of a desire to bully.