First, I must identify myself as a nonbeliever and on that basis you may chose to disregard whatever I say.
In any case, I think if you believe something—as you clearly do—you should state it forthright. As you have done.
I am in no position to judge your theological point. However, I think you made a mistake in attributing evil intent to the Jehovah’s Witnesses. Do you really believe that were intentionally trying to send you and your wife and others straight to hell? Or do you think that their mistaken beliefs would, unintentionally, potentially create that unfortunate result?
My view is that most people have good intentions even when their actions are ill conceived and may result in bad outcomes. Yes, when a person is angry or fearful, his judgement is clouded and he may very well have evil intentions. But that does not appear to be the case with these affable house guests.
My view is: stand up for your beliefs, but do not assume evil intent on behalf of others unless you have compelling reason to do so.