One thing I've pointed out in casual conversation with my Witness acquaintances is that their attempt to redefine the term "generation" reduces Jesus' statement to nonsense.
This can easily be seen with a simple exercise.
1. Define your terms
2. Paraphrase the scripture using those terms.
For example, prior to 1995 this is how the Witnesses defined their terms:
"Pass away" = Die from old age
"Generation" = Those living when the sign commenced
"All these things" = The entire sign including Armageddon
Plugging these terms in gives us the following:
"Truly I tell you that Those living when the sign commences will not Die from old age until The entire sign including Armageddon occurs."
The issue here is not whether this interpretation is right or wrong (I personally think it is wrong) The point is that the sentence at least makes sense.
After 1995 the Witnesses defined their terms differently:
"Pass away" = Be executed at Armageddon
"Generation" = Those living during the sign who take no note
"All these things" = The entire sign including Armageddon
"Truly I tell you that Those living during the sign who take no note will not Be executed at Armageddon until all The entire sign including Armageddon occurs."
So in other words, the wicked generation won't be destroyed at Armageddon until Armageddon?
The temporal preposition "Until" requires posteriority of the conditions it introduces. When that doesn't happen the result is the sort of meaningless tautology you see above.
I think this causes discomfort for many Witnesses at a level they can't express in words because they dont' actually think about what they're taught.