my post to Dr. Long on Acts 11:18 and Gentile Salvation

Over at the blog of NT scholar Dr. Phillip J. Long, I posted the following questions and concerns about why the followers of the apostles indicate in Acts 11:18 that Gentile salvation is some new shocking unexpected theological development :

Dr. Long, 

I have argued for years on the basis of Acts 11:18 that God granting to Gentiles the repentance that brings salvation, must have been some new unexpected shocking thing to the Christians listening to Peter give that speech. 

What exactly is Peter's audience discovering? 

That Gentiles can be saved? 

Or the more nuanced discovery that the Gentile salvation they already knew to be available, doesn't require two steps, but only one? 

The wording in 11:18 is, IMO, too simple to justify the latter more nuanced interpretation, so IMO this church is startled to learn that Gentiles can be saved period.
This of course is a serious problem given that these Christians are the results of the labors of the 12 apostles, who surely must have known that Jesus had a major mission to the gentiles (Mark 1:45, Matthew 4:15, 12:21, Luke 2:32). 

Indeed, the risen Christ insisted that his teachings were the basis of all future Gentile salvation/discipleship in the Great Commission, Matthew 28:20. 

So why was Gentile salvation so controversial to these followers of the apostles?
Did the apostles, after being "amazingly transformed" by seeing a resurrected Jesus ordering them to preach salvation to the Gentiles (Matthew 28:20), and after being miraculously filled with the Holy Spirit (Acts 2), end up neglecting the Gentile aspect of the gospel to the point that their immediate followers find Gentile salvation to be this unexpected shocking theological development, as they apparently conclude in Acts 11:18? 

Can we really fix these problems with a quick "the apostles just didn't get it" ? 

If Jesus physically appeared to me and I ran around on the earth with him for three years, then saw him risen from the dead and ordering me to do certain things, it doesn't make sense that I'd be slow to obey or understand what had been drilled into my head for those prior three years.
So it would appear that the anti-Gentile sentiment was not just some questionable misunderstanding by the followers of the apostles, but went back to the apostles themselves (Galatians 2:9, limiting their evangelism to just the Jews, in contradiction to the risen Christ's direct command that they, that is, the 11 original apostles, do the work of the Gentile ministry).