"Any objective reading of the gospels makes it plain that Jesus believed his parousia would happen within the lifetime of his generation."
You might want to read a 'basic' book about the gospels. Any objective reading of the gospels makes it plain clear that Jesus believed the destruction of the temples and of physical jerusalem was going to happen within the lifetime of his generation.
Consider this....Matt 24:1-3 - Jesus is walking w/ his disciples and they show him "the buildings of the temple". Jesus tells them, "Truly I saw to you by no means will a stone be left upon a stone and not thrown down".
So Jesus says those buildings are going down! Then the disciples ask, "When will this be?(TIME PERIOD 1)"
NOW HERE IS THE TRICKY PART!!! If you only read Matt, Jesus doesn't answer the question right then and there, but instead the disciples as 2 other questions....."What will be the sign of your presence (TIME PERIOD 2)", "What will be the sign of the conclusion of the system of things (TIME PERIOD 3).
If you read the other gospels, you can know for a fact that Jesus was not saying they would all happen at the same time. Here are some statements of proof on that....
Acts 1:7 - "It does not belong to you to get knowledge of the times or seasons which the Father has placed in his own jurisdiction." - does that not go against nations against kingdom, wars, signs, etc, unless ofcoarse those were speaking about something else.
Luke 19:41-44 Jesus gives deep details about what would happen to Jerusalem in 70 CE, IN THAT GENERATION...."And when he got nearby, he viewed the city and wept over it, 42 saying: “If you, even you, had discerned in this day the things having to do with peace—but now they have been hid from your eyes. 43 Because the days will come upon you when your enemies will build around you a fortification with pointed stakes and will encircle you and distress you from every side, 44 and they will dash you and your children within you to the ground, and they will not leave a stone upon a stone in you, because you did not discern the time of your being inspected.”
In Luke 21 things are a little different then in Matt 24. In Matt 24:9 people are killed. (the early christians and apostles were killed and martyred). In Luke 21:12-19 however, if you read closely you'll see it's describing something different, people are delivered up, betrayed by family, and supposedly killed but not a hair on their head perishes, and by 'endurance' they aquire their souls. They are not actually killed like the first group but disfellowshipped. That's how they are killed yet not a hair on their head perishes.
That's also spoken more detailed in Mark 13:9-13 about child against parents and parents against children, which is exactly what happens with shunning and such in the JW religion, yet nobody physically kills the other.
In Mark 13:7,8 Jesus brings out how the wars and world's problems will happen but they are NOT the end. It's merely the start of bad things.
In Mark 13:32 he clearly says nobody knows when it will come.
Also go back to Matt 24. You'll see how this was all a bit scrambled up. In Matt 24:34 and 35 you see teh statement about the generation. Which is speaking about the destruction of Jerusalem.
Then right after, in Matt 24:36-39, THAT is speaking about the real end, nobody knows the day or hte hour and how bad would things be? Actually it describes things as being normal, people drinking, marrying, etc. When it actually comes it does come as a surprise, not in the midst of wars and such. That's also why you have the scripture about peace and security. Things will seem fine.
Lastly, I did forget a MAJOR important scripture.....Jesus foretold the destruction of Jerusalem, and he also gave a time limit for how long it would remain destroyed/trampled by nations.....
Luke 21:24 (continuing with what happened in 70CE "and they will fall by the edge of the sword and be led captive into all the nations, and Jerusalem will be trampled on by the nations, UNTIL the appointed times of the nations are fulfilled." (Makes you wonder if the restoration of Israel to Jews after WW2 is tied to that.)
In summary what he said was sort of scrambled and many different time periods put together. If you read all the gospels and sort it out, you'll see he foretold that the temple and Jerusalem would be destroyed in THAT generation and the disciples in THAT time would be martyed. That jerusalem and jews are scattered and put into other nations until the end of the gentile times. That there would be wars and food shortages, etc, and all of that is NOT the end. That in future timeperiod his people would be killed by disfellowshipping, families turning on each other. Many would claim to be anointed or to follow them for Christ (like Rutherford and other false teachers) and to NOT follow them. That nobody knows when the end will finally come but it will be in a time when things are calm and least expected.