Gal 1:8 But even if we or an angel from heaven should preach to you a gospel contrary to the one we preached to you, let him be accursed.
Gal 1:9 As we have said before, so now I say again: If anyone is preaching to you a gospel contrary to the one you received, let him be accursed.
To your credit, RM, you at least provided a passage. However you provide no connection between Paul's teaching here and Preterism. The context makes it quite clear what the false gospel is. It is teaching that is contrary to the true gospel. In this immediate context, the first dozen verses or so of this epistle, we have several essentials of the gospel mentioned. Just a few:
Our Savior
raised from the dead, vs. 1,
Christ
gave himself for our sins, vs. 4, and
Rescued us from this present evil world, vs.4.
He
called us by His grace, vs. 7.
While this is not a complete description of the gospel - that was not the intention - it
does give us an indication of what was in Paul's mind when he then warned against the enemies of this same gospel. There is no mention at all here of the
timing of Christ's coming, nor of Christ's
nature at His coming (that is, the Parousia).
It is interesting how this verse is used as a holy two-by-four against whatever the user sees as his enemies. Arminians use it against Calvinists (and vice versa).
More accurately, orthodox Christians use it against cultists who deny essential teachings like the deity of Christ. This is a proper use of the passage mainly because those who deny Christ's deity also deny the gracious nature of the gospel. Cultists, like the Judaizers that Paul was targeting here, make the grace of Christ of no effect with their formula of "God And ___". What is filled in the blank varies from cult to cult, false religion to false religion. But the mere existence of
any additional item besides grace, makes the grace of Christ - and the
Cross of Christ - of no effect.
There is
nothing here about Preterism.
Preterism teaches another Jesus. The gospel includes a future, literal, and physical return of Christ.
And after He had said these things, He was lifted up while they were looking on, and a cloud received Him out of their sight. 10 And as they were gazing intently into the sky while He was departing, behold, two men in white clothing stood beside them; 11 and they also said, "Men of Galilee, why do you stand looking into the sky? This Jesus, who has been taken up from you into heaven, will come in just the same way as you have watched Him go into heaven." (Acts 1:9-11).
This passage teaches the manner of Christ's Parousia, not His nature. "He will come in just the same way". In the same way that "He was taken" He was to have returned.
How was He taken? "A cloud received Him out of their sight."
That is how He was to return.
One can try to explain away these verses all they want. But the B-I-B-L-E is very clear. And when you have to start playing spiritual gymnastics and use eisegetical measures to be able to comfortably stick this heresy then you one has lost their way. Just as bad as the idea that God creates some men just to damn them.
We see what we want to see. Actually, what you write here reminds me of myself - especially back in my BJU days in the 70s. I was so sure that I was totally in the right when it came to these matters.
But I have since done a lot of Bible studying and a lot of unstudying too (which is harder to do). Even though I was irked by comments made by people I was pretty sure were unsaved, I kept some of the points they made in mind, studying them out Scripturally when I had opportunity later. I hope you will too.