I really want to avoid playing definition and semantics games.
You may be playing such games, but I am not. I have grounded my assertions in Scripture, not semantical maneuvering.
Whether we call them "baptism of" or "being filled with", what matters is that we both agree that there are special moments when the Holy Spirit can come over someone in a notable way, empowering them for witnessing, and these special moments can take place more than once. That's undeniable from Acts 4:29-31, right?
I already addressed this. It is important to distinguish between being baptized in the Spirit, which is to be born-again into Christ (
Romans 6:1-10; Romans 8:9-11; Titus 3:5; 1 John 4:13, etc.), from being merely filled by the Spirit. Scripture indicates one is born-again by the Spirit only once, whereas one may be filled by the Spirit many times throughout one's life. To get this wrong is to begin down the road of the hyper-charismatic, some of whom claim as many as
twelve different possible baptisms in the Spirit - among a host of other cockeyed false doctrines.
Acts 4:29-31 does not describe the same event as in
Acts 2 where the gathered disciples of Christ become the first born-again children of God. In the
Acts 4 instance, the apostles were simply filled - as the account says - with the Spirit, not spiritually-regenerated, as happens at conversion.
Now, regarding your claim that the apostles became born again in Acts 2: there is no verse in Acts 2 that says that the 120 became born again at Pentecost and hadn't been born again up until that point. You appear to base your claim on the assumption that the apostles received the Holy Spirit for the first time in Acts 2. However,
John 20:21-23 tells us otherwise:
21Again Jesus said, “Peace be with you! As the Father has sent me, I am sending you.” 22And with that he breathed on them and said, “Receive the Holy Spirit. 23If you forgive anyone’s sins, their sins are forgiven; if you do not forgive them, they are not forgiven.”
Had Jesus died on the cross for the sins of the disciples when he did what he did in
John 20:21-23? Had atonement been made for the disciples which was utterly necessary for their justification, sanctification, redemption and acceptance by God?
The fact that the disciples were not yet born-again would explain why, in
Acts 2, the Spirit came again upon these same disciples - from whom, obviously, the Spirit had departed since the event of
John 20:21-23 - as the Spirit did with individuals in OT accounts (ie. Samson) who also were not born-again.
Furthermore, there is no reason to doubt that the 120 disciples in the upper room were already water baptized and believed in Jesus as their messiah by the moment Acts 2 happened.
Baptism - or, at least, ritual purification - was not uncommon among the Jews in OT times. But their "baptism" did not secure salvation for them. It couldn't.
Only the sacrifice of the Lamb of God could save in the manner of the New Covenant, spiritually-regenerating a person (
Titus 3:5) and making them a temple of the Holy Spirit (
1 Corinthians 6:19-20). And as accounts of Acts indicate, merely being baptized by John the Baptist and believing in Christ as Messiah did not spiritually-regenerate people; only by baptism of the Spirit - being born spiritually - was a person fully adopted by God and made one of His children.
Despite all of that, are you seriously saying that none of them was already born again when Acts 2 took place?
This is what the Bible plainly indicates. See above. There is no spiritual regeneration apart from the atoning work of Christ at Calvary. It is, in my view, a kind of blasphemy to suggest otherwise.
Acts 4:12 (NASB)
12 "And there is salvation in no one else; for there is no other name under heaven that has been given among men by which we must be saved."
1 Corinthians 1:30-31 (NASB)
30 But by His doing you are in Christ Jesus, who became to us wisdom from God, and righteousness and sanctification, and redemption,
31 so that, just as it is written, "LET HIM WHO BOASTS, BOAST IN THE LORD." 
