I suspect that many posters and those who respond to their posts are not fully familiar with either church history or the Bible so they are not as able to respond to questions or challenges to their posts and responses.
I am just a now long-retired high school English teacher. Nevertheless, I have been reading the Bible seriously since 1953. I still am studying the Bible. I learn something new to me almost every day.
Here is some Scripture that I believe directly addresses your challenge to cite “scripture to support that idea what anyone who rejects the Son is still in communion with God?”
Rom 11:25 For I would not, brethren, that ye should be ignorant of this mystery, lest ye should be wise in your own conceits; that blindness in part is happened to Israel, until the fulness of the Gentiles be come in.
Rom 11:26 And so all Israel shall be saved: as it is written, There shall come out of Sion the Deliverer, and shall turn away ungodliness from Jacob:
Rom 11:27 For this is my covenant unto them, when I shall take away their sins.
Rom 11:28 As concerning the gospel, they are enemies for your sakes: but as touching the election, they are beloved for the fathers’ sakes.
Rom 11:29 For the gifts and calling of God are without repentance. (KJV)
Note particularly Romans 11:28,
Rom 11:28 As concerning the gospel, they are enemies for your sakes: but as touching the election, they are beloved for the fathers’ sakes.
Unbelieving Israel is still beloved for the fathers’ sakes.
I have carefully compiled what are called “cross references” for every verse in the Bible. I present them in my book, The New Treasury of Scripture Knowledge, and I have further expanded those in my digital resource, the Ultimate Cross Reference Treasury.
As I compiled these verses, I retained the verses of my sources, whether I agreed with them or not, so some cross references do not agree with what I know that Scripture actually teaches.
For Romans 11:28, here is the most relevant portion of the cross references I have for the key words “they are beloved” and the key words “for the fathers’ sake”:
they are beloved. Rom 9:5; Rom 9:25, Gen 26:4; Gen 28:14, Exo 20:6, Lev 26:40, 41, 42, Deut 4:31; *Deut 7:7; *Deut 7:8; Deut 8:18; Deut 9:5; +*Deut 10:15; Deut 23:5, Psa 105:8, 9, 10, 11, *Isa 44:21; Isa 49:15, *Jer 11:15; Jer 31:3, Hos 11:9, Amos 9:8, *Mic 7:20, Zec 1:17, *Mal 1:2; +*Mal 3:6, Mrk 10:14, Luk 1:54, 55; Luk 1:68, 69, 70, 71, 72, 73, 74, 75.
for the fathers’ sake. Rom 3:2; Rom 9:5; *+Rom 15:8, +*Exo 2:24; Exo 33:13, *Deut 7:8, Isa 63:8, *Dan 9:15, 16, 17, 18.
At the moment I see two exceedingly crucial cross references given for the key words “they are beloved”:
Leviticus 26:40-42
40 If they shall confess their iniquity, and the iniquity of their fathers, with their trespass which they trespassed against me, and that also they have walked contrary unto me;
41 And that I also have walked contrary unto them, and have brought them into the land of their enemies; if then their uncircumcised hearts be humbled, and they then accept of the punishment of their iniquity:
42 Then will I remember my covenant with Jacob, and also my covenant with Isaac, and also my covenant with Abraham will I remember; and I will remember the land.
King James Version
Malachi 3:6
6 For I am the LORD, I change not; therefore ye sons of Jacob are not consumed.
King James Version
The “sons of Jacob” are “not consumed” because God is not finished with the nation of Israel. God has promises to Abraham in the Abrahamic Covenant which have not yet been fulfilled, but they will be fulfilled to the person (Abraham) and nation (Israel) to whom the promises were originally given (Acts 7:5. Isaiah 55:3).
Act 7:5 And he gave him none inheritance in it, no, not so much as to set his foot on: yet he promised that he would give it to him for a possession, and to his seed after him, when as yet he had no child.
My note on a portion of this text:
him. The point is, that the promise was made personally to Abraham that he would himself inherit the promised land, but Abraham himself never personally possessed the land God promised to him. It is for this reason that God, who cannot lie, must resurrect Abraham and bring him personally into the promised land in order for the Abrahamic Covenant to be fulfilled. How many Bible scholars have failed to notice the explicit statement of Scripture here, which declares that Abraham did not receive the inheritance, and have taught the opposite, and worse, have spiritualized and transformed the covenants into something they were never meant to be, taking to themselves or the church the blessings promised to Abraham and the Jews, but very carefully leaving the curses to Israel, literally interpreted at that (see related notes at **Jos 21:43 note. **1Ki 4:21 note. Isa 60:21 note. Jer 33:21 note). +*Mat 8:11; +*Mat 8:12, +*Rom 4:13.
Now for Isaiah 55:3,
Isa 55:3 Incline your ear, and come unto me: hear, and your soul shall live; and I will make an everlasting covenant with you, even the sure mercies of David.
Many Bible readers are not familiar with just what “the sure mercies of David” are or refer to. Many modern Bible translations actually obscure rather than assist the reader’s understanding of this crucially important Bible text.
In brief, the “sure mercies of David” are a reference to the provisions of the Davidic Covenant. Those referenced are unconditional and are not yet fulfilled but God has promised that they will be.
Now, as for scholarly research I have just completed reading about this subject which goes in depth into the history behind this issue, I highly recommend reading this resource:
Pettegrew, Larry. 2020. Forsaking Israel: How It Happened and Why It Matters. The Woodlands, TX: Kress.