I see where Scooby was coming from. Russell WAS speculating, but out of a sincerity, perhaps. Rutherford was just about running the show and manipulating everyone to get what he wanted, from what I have observed of his writings, his actions and reports of his character.
So, it is worse than speculation-even of making dubious(delusional?) claims to be being led by God. Rutherford was not just speculating and his sins in the org were not based in delusion or even really bad math! He was just playing people. Speculation wrongs are the least of his wrongs against JWs (bible students!).