How about just reading what the Word says?
{29} "Woe to you, scribes and Pharisees, hypocrites! [Was He talking to any other generation here???] For you build the tombs of the prophets and adorn the monuments of the righteous, {30} and say, 'If we had been living in the days of our fathers, we would not have been partners with them in shedding the blood of the prophets.' {31} "So you testify against yourselves, that you are sons of those who murdered the prophets. {32} "Fill up, then, the measure of the guilt of your fathers. {33} "You serpents, you brood of vipers, how will you escape the sentence of hell?
{34} "Therefore, behold, I am sending you prophets and wise men and scribes; some of them you will kill and crucify, and some of them you will scourge in your synagogues, and persecute from city to city, {35} so that upon you may fall the guilt of all the righteous blood shed on earth, from the blood of righteous Abel to the blood of Zechariah, the son of Berechiah, whom you murdered between the temple and the altar. {36} "Truly I say to you, all these things will come upon this generation. Matthew 23:29-36 (NASB)
These were the same folks asking Him for a sign earlier in the gospels and here He is, again, confronting them.
"This generation" clearly refers to those people who were standing right there in front of Him!
This is the same generation mentioned in the parable of the fig tree (and all the trees in Luke). It was the generation that crucified Him and persecuted to death the apostles He sent to them!
And - once more - how do we know this for sure?
{24} "And in her was found the blood of prophets and of saints and of all who have been slain on the earth." Revelation 18:24 (NASB)
Rome killed NT witnesses for Jesus. Babylon may have killed a prophet or two. Only one city ever killed both the prophets of the OT and the apostles of the New:
Jerusalem.
It was judged in 70 AD for this, just as it had been in 587 BC.
Not my words: Christ's.