These false witnesses were making the claim that Stephen was speaking against the (laws of Moses and the holy place). In other words, they were making the claim that Stephen was speaking against the laws of Moses and the Holy Temple. For this they accused Stephen of speaking blasphemous words.
When reading the New Testament we have to remember it was the ending of the old age of the Mosaic, laws. And the starting of the age of grace in Christ. The Jews had the Torah of Moses and the Holy Tabernacle later the Temple, which represented (the Shekinah of glory) for over 15.000 years.
They were still hanging on to these Judaistic rituals that had been so much a part of their life and the change did not happen over night. It was extremely difficult for the Jews to accept the superiority of the New Covenant Christ offered. It was especially hard for them to make a clean break with the old Mosaic customs. The Jews held both Moses and their Temple in high esteem and we can understand why.
Solomon gave orders to build a temple for the Name of the LORD, and a royal palace for himself. He conscripted seventy thousand men as carriers and eighty thousand as stone cutters in the hills and thirty-six hundred as foremen over them. Solomon sent this message to Hiram king of tire: "Send me cedar logs as you did for my father David when you sent him cedar to build a place to live in. Now I am about to build a temple for the Name of the LORD my God and to dedicate it to him for burning fragrant incense before him, for setting out the consecrated bread regularly, and for making burnt offerings every morning and evening and on Sabbaths and New Moons and at the appointed feasts of the LORD our God. This is a lasting ordinance for Israel. "The temple I am going to build will be great, because our God is greater than all other gods. But who is able to build a temple for him, since the heavens, even the highest heavens, cannot contain him? Who then am I to build a temple for him, except as a place to burn sacrifices before him? (2 Chronicles 2 :1-5)
What the Jews refused to see was 'Heaven is God’s throne, And earth is His footstool. (Act 7:44- 49) As long as there was a tabernacle or temple on earth, there was a material reflection of God’s for the Jews to see. This was especially hard to let go since the Temple was still standing and the priests were continuing to minister. Many continue to believe in and support the Judaistic type of an earthly temple. They were still hanging on the Judaistic rituals that had long been a part of their life.
What is it about the (claims against Stephen) in these verses that has been completely over look for so long? Please ask yourself the following question. If the parousia of Christ is, as you and I have been traditionally taught, a literal world ended event. How in the world could these people falsely accuse Stephen of saying (Jesus the Nazorean will destroy the Holy Temple and change the customs that Moses) handed down to them?" It is really important not to overlook these very important “time statements” here.
It is not important if these false witnesses were making false claims against Stephen or not. The point is these people had another concept of the (timing and nature of the parousia of Christ) and they made these statements after Jesus had long been resurrected and ascended to heaven. (Mark 6:19-20)
The real purpose of this whole episode, was to accuse Stephen of the crime of saying Jesus will destroy the Temple and the Mosaic law handed down to them. How is it possible for Jesus to return and destroy the Temple and change customs of the Mosaic law handed down to them in our day when the Temple and their customs of keeping the law have long been destroyed?
Stephen or his accuser tied the parousia of Christ and the destruction of the temple along with the end of the Judaistic (age or world). Where did they get that idea? Jesus mention, the destruction of the temple at the Mount of Olives. Matthew 24:1-3 Then Jesus went out and departed (from the temple), and His disciples came up to show Him the (buildings of the temple). And Jesus said to them, "Do you not see all these things? Assuredly, I say to you, (not one stone shall be left here upon another, that shall not be thrown down)." Now as He sat on the Mount of Olives, the disciples came to Him privately, saying, "Tell us, when will these things be? And what will be the sign of (Your coming, and of the end of the age)?" (emphasis added)
Please notice here that the disciples also tie the destruction of the temple along with the end of the Judaistic (age or the end of the Mosaic, customs). Not only had Jesus actually said the Holy Temple would be destroyed, he predicted the entire destruction of Jerusalem along with his Parousia. (Luke 21:5-27).
The destruction of the Temple represented a major crisis for Judaism because of all the Temple had signified for them. It meant the end of the customs of the Mosaic law handed down to them and the Presence of God the Shekinah of glory, the place of the daily sacrifice. Israel’s place in election, etc.
Stephen defense was not a response to refute the charges against him, but takes the form of a discourse that reviews God's word to Israel and leads to a prophetic declaration a plea for the hearing of the words.