"It sounds like he got it wrong, doesn’t it? All this seems to be happening virtually at once, from the fall of the city to the return of Christ. A lot of skeptics say so."
Gilson make it sound like only internet atheists have argued this. No, this is what many biblical scholars of various theological stripes have concluded (perhaps the majority, depending on who you ask), and even liberal Christians like Thom Stark agree that this is the case.
"In this passage, though, that’s not the case. Look at verse, 24, which I omitted before, and belongs at the end of the first paragraph above:
They will fall by the edge of the sword and be led captive among all nations, and Jerusalem will be trampled underfoot by the Gentiles, until the times of the Gentiles are fulfilled.How long did Jesus expect that interim period to last? Long enough for the Jews to be dispersed among all nations; long enough for the “times of the Gentiles” to be fulfilled. A while, in other words–an indefinite while, that is. I don’t think Jesus can be accused here of getting this wrong."
There's nothing here that logically required an "indefinite while" to had taken place before the return of Jesus: possibly allowing for reasonable hyperbole (but not requiring it), The Jews could have been led captive (not "dispersed"; captivity is the verbage used by the text) among "all nations" by the end of the 2nd Temple era or shortly after (which was roughly a 40 year period). Mainstream scholars (e.g, Allison, Ehrman) have argued that the "times of the Gentiles" was fulfilled at the destruction of the 2nd Temple, which seems to be the era Jesus has in mind here, given the overall context and theme. Importantly, Jesus says in verse 32 that their generation (that of the disciples, who he's speaking to) "will not pass away" until "all has taken place." (Elsewhere, he says all will not "taste death" until they see the "Kingdom of God.")
"That’s especially true if we add Matt. 24:14 into the mix"
The known world wasn't as large to Jews in Jesus' day. So a command to preach throughout "the whole world" and "to all nations" isn't a problem for the Failed Apocalyptic Prophet thesis. What apologists try to do here is make "preach throughout the world" a temporal indicator, when Jesus himself already has given several clear temporal indicators.
Later on, when an interlocutor makes reference to the "this generation" passage, Tom says this:
"The rest of the paragraph (ESV) says,
And he told them a parable: “Look at the fig tree, and all the trees. As soon as they come out in leaf, you see for yourselves and know that the summer is already near. So also, when you see these things taking place, you know that the kingdom of God is near. Truly, I say to you, this generation will not pass away until all has taken place. Heaven and earth will pass away, but my words will not pass away.So there is some set of signs that indicate the season of his return is arriving. What are those signs? Go back one more paragraph, and you’ll find that there’s a section where his topic seems to have shifted somewhat. He could be talking about the fall of Jerusalem, and the disciples could have naturally interpreted him that way, but it’s also not an unnatural interpretation to suppose that he could be shifting to another time frame. :
And there will be signs in sun and moon and stars, and on the earth distress of nations in perplexity because of the roaring of the sea and the waves, people fainting with fear and with foreboding of what is coming on the world. For the powers of the heavens will be shaken. And then they will see the Son of Man coming in a cloud with power and great glory. Now when these things begin to take place, straighten up and raise your heads, because your redemption is drawing near."
But this is an unnatural interpretation, because Jesus is telling his disciples-his audience, not some unnamed generation reading a book, unknown millennia into the future- "when these things begin to take place, straighten up and raise your heads, because your redemption is drawing near." Moreover, Mark and Matthew are even clearer: in Mark, the Son of Man comes "after that tribulation," but still "in those days (Mark 13:24)." Matthew makes things even worse: "immediately after the tribulation of those days..." (Matthew 24:29). 
"Not only that, but if you back up even further to Luke 21:10-19, you’ll see that Jesus is speaking of a whole range of events that seem to take place over an extended period of time, beginning with the disciples’ lifetimes, but not containable within that short time frame."
But a careful reading shows that this all happened before the temple fell again in 70 CE. Nothing described here is not containable within the apostle's generation, Tom's assertion to the contrary notwithstanding. Perhaps Tom had in mind a more widespread persecution of Christians that took place in later centuries, but as Paul and the book of Acts can attest, persecution also took place early on.
"For these reasons, I conclude that “this generation” does not refer to the generation of those who were standing there listening to him, but to the generation that sees the final signs coming together, as he refers to throughout the chapter."
And it is for these reasons Tom's defense of Jesus' infallibility doesn't appear to stand up to close scrutiny. If we had only the few passages that have been discussed on hand, the Failed Apocolyptic Prophetic Thesis would fair pretty strong. Jesus fits well within his apocalyptic era further elucidated by the Qumran community, et al. But the Failed Apocolyptic Prophet Thesis accounts for a much wider range of data, summarized beautifully by the Ex-Apologist here: http://exapologist.blogspot.com/2007/10/one-of-main-reasons-why-i-think.html
Readers further interested in the apocolypticism of Jesus would do well to consult the works of Thom Stark, John Loftus, Dale Allison, Schweitzer, et al.
 Credit goes to Thom Stark for this enlightenment.