Scriptures? How about Jeremiah 25: 10 and 11:
This whole land shall become a ruin and a waste, and these nations shall serve the king of Babylon seventy years. Then after seventy years are completed, I will punish the king of Babylon and that nation, the land of the Chalde'ans, for their iniquity, says the LORD, making the land an everlasting waste.
JWs teach that in 539 BC, Babylon was overthrown by Cyrus and Belshazzar was killed. Cyrus then frees the Jews and, after finally getting motivated, they return and arrive back in Jerusalem in 537 BC, ending the 70 years, which they claim began in 607 BC.
However, how can this be possible in light of Jeremiah 25? It says that after 70 years are completed, the king of Babylon will be punished. So, 70 years were completed already when the king of Babylon was punished in 539 BC. Therefore, 70 years could not have ended 2 years after he was killed.
Also says these nations will serve the king of Babylon for 70 years. This doesn't only apply to Judah, but other nations as well. But was Judah serving Babylon before the final seige? Look at Kings 24 and 2 Chronicles (last 2-3 chapters - I forget exactly where). See that other kings were vassals (servants) to Babylon before Zedekiah even began to reign. And they also rebelled. How can you rebel against somebody who you do not serve? So, "serving" must have started before the end of Zedekiah's reign. Look at Zedekiah himself. Nebuchadnezzar put him on the throne and even changed his name to Zedekiah. If that doesn't show you who's boss, I don't know what does.
Their chronology simply does not jive with the Bible.
What's more, look at Daniel 9:2, Zechariah 1: 12, and Zechariah 7:5. This is a second 70-year period that DID start at the end of Zedekiah's reign. Or at least when Babylon came to lay siege to Jerusalem. But this one ends in the time of Darius, who began ruling in 522BC. If you back up 70 years from the time of these scriptures, you land right at about 588 BC, which is when Nebuchadnezzar laid siege to Jerusalem (or so history says). This proves the "secular" historical chronology.
Note that there is also a third 70-year period mentioned in Isaiah, but that is about Tyre. It is not to be confused with the 70-year periods concerning Jerusalem.
I think you can argue many points or how people act or whatever. Some of it can be denied to the brainwashed mind. You can say look at how people treat each other. They can say, "that's biblical", or "it's only local - they're just not acting like they're supposed to".
I think, at least for me, it came down to knowing what they teach is flat-out wrong - and they always taught me, if your religion is wrong, you need to leave it. Then, after investigating, seeing how they lied to give their false claims weight. Look at all the false statements about how bad things have been since 1914. Look at all the discrediting they do of secular chronology as if to say none of it is reliable, when in fact, they have ample evidence from authors like Carl Olaf Johnson that the 1914 thing is way off.
Two excellently researched books are The Gentile Times Reconsidered and Last Days, When?, both by Carl Olaf Johnson. The Gentile Times goes into all the proof that the WTBS chronology on 607BC is wrong, with proofs from Babylonian sources and from the Bible. The Last Days book goes to the other end of that 2520 year period, 1914 and goes into all the claims that say earthquakes, food shortages, wars, etc. are worse since 1914. I personally found them both fascinating, but the Last Days book is the lighter read of the two. It handles each "sign" chapter by chapter, providing modern quotes and evidence. Some of the evidence concerning archeaology in Gentile Times would probably get tiring if you're not into it.