First lets look at the history of "Jew".
*** it-2 p. 73 Jew(ess) ***
The name is not used in the Bible account prior to the fall of the ten-tribe kingdom of Israel. The southern kingdom was called Judah, and the people were called sons of Judah or the tribe of the sons of Judah. The first one to use the name Jews was the writer of the books of Kings, doubtless Jeremiah, whose prophetic service began in 647 B.C.E. (See 2Ki 16:6; 25:25.) After the exile the name was applied to any Israelites returning (Ezr 4:12; 6:7; Ne 1:2; 5:17) and, finally, to all Hebrews throughout the world, to distinguish them from the Gentile nations. (Es 3:6; 9:20)
Now the word Hebrew.
*** it-1 pp. 1065-1066 Hebrew, I ***
As the above texts show, the designation “Hebrew” was already familiar to the Egyptians in the 18th century B.C.E. This would seem to indicate that Abraham, Isaac, and Jacob had become quite well known over a wide area, thus making the appellative “Hebrew” a recognizable one. When Joseph spoke of “the land of the Hebrews” (Ge 40:15) to two of Pharaoh’s servants, he doubtless referred to the region around Hebron that his father and forefathers had long made a sort of base of operations. Some six centuries later the Philistines still spoke of the Israelites as “Hebrews.” During the time of King Saul “Hebrews” and “Israel” were equivalent terms. (1Sa 13:3-7; 14:11; 29:3)
Hebrew and Jew are names for the same people at different times. Both involve being descendants of Abraham, Isaac, and Jacob. While Esau was from Abraham, the term has never been applied to him, nor to any of the descendants of Lot, Abraham's nephew.
With the destruction of the 10 tribe kingdom of Israel, the term reflected the fact that the main surviving tribe, Judah, was now dominate, and the name "Jew" means "of the tribe of Judah".
What the man is arguing is that what is called "Jews" today are "invaders" on the rights of Abraham. That is clearly a false premise.
The words of Peter and Paul settled the issue. With the end of the special status that Jews had under the Law, all mankind are equal before Jehovah, and acceptable to him as his servants.
(Romans 1:16-17) 16 For I am not ashamed of the good news; it is, in fact, God’s power for salvation to everyone having faith, to the Jew first and also to the Greek; 17 for in it God’s righteousness is being revealed by reason of faith and toward faith, just as it is written: “But the righteous one—by means of faith he will live.”
(Romans 10:11-12) 11 For the Scripture says: “None that rests his faith on him will be disappointed.” 12 For there is no distinction between Jew and Greek, for there is the same Lord over all, who is rich to all those calling upon him.
In a way though it is true the Jehovah's Witnesses are "controlled" by the "Jews".
(Galatians 6:15-16) 15 For neither is circumcision anything nor is uncircumcision, but a new creation [is something]. 16 And all those who will walk orderly by this rule of conduct, upon them be peace and mercy, even upon the Israel of God.
With the founding of the Christian Congregation at Pentecost a new nation was formed, not out of any one tribe or nation, and with a everlasting future ahead. These "spiritual Jews", Christ's brothers, do have the authority to care for Christ's interests and his followers.
The problem the man has is his bigotry, and I doubt any amount of reasoning will sway him.