I don't think the more mainstream Religions ever considered "Russellites" or Bible Students as they were probably more widely known as a Bona Fide religion. There are plenty of Articles and Pamphlets opposing Russell's views, some from Bible Students themselves.
Rutherford was taken apart by the same sort of thing, I remember reading a pamphlet produced by a Church of England Minister that tore in to Rutherford's nonsense that was published just about the time they adopted the name Jehovah's Witnesses. I reckon most people of the time agreed with much of what he wrote. He started off by taking the piss out of their frequent change of name.
I do think the general Public looked upon them, even in my youth, as just another sect, with maybe some reserve as to the strange views, but we were accorded respect, and often a hearing ear, as we door knocked. I do not remember at any time a great number who challenged the Bona Fides. But, I do remember one old gentleman who told me to study Russell's activities, he mentioned the " Miracle Wheat", and the fact that in his view Russell wanted to start a new religion, not to actually get back to Primitive Christianity.
So not all of the Public, even then, in the 1950's, looked upon them as genuine.