Oh, I quite agree. That's one reason why I neither stand there debating with them, nor read their literature.
My point, though, is that if I regard the JWs as annoying pests, or as nuisance do-gooders who think they know what's best for me and are determined that I have it -- it gets me upset. And I bet it does you, too, if you're honest with yourself about it.
I remain much calmer if I think of them as sincere, but misguided, folks who are trying in their own way to help their fellow human beings. I have no interest in receiving the type of help they wish to provide, but if that lack of interest causes me to become angry and turn them away harshly, in the end I have harmed only myself.
Now if I could only persuade myself to take the same attitude toward the environmental activists that go door-to-door in my neighborhood (after driving here in a Suburban!)...