I just blew out three paragraphs in which I explained why I disagree with the above statement. We've gone over this topic before.
IMO, the important thing is that when we think of God from the standpoint of Being, we agree that He is One. Thus, despite the multiplicity of persons in the triune Godhead, Christians are monotheists. From my perspective, the most logical way to resolve the paradox of three divine persons sharing one divine being is to hold instead that there is only one person in the Godhead, and that Jesus is united to Him in Spirit rather than in Being.
All of which gets too bogged down in the theological definitions, and misses the overall Truth. What does it even mean to talk about "God's Being", anyway? As soon as we try to put it into words, we fail. We cannot understand God as He is. All of our words about Him at best point to the Truth, which cannot be known intellectually, only experienced in relationship with Him.
We agree that God is One. I'll further agree with you that Jesus is One with God. And still further I agree that we can be One with God, too. Say more than this, and we get into intellectual debate and lose sight of knowing, which can only be attained through relationship with Him.
And in that day will I make a covenant for them with the beasts of the field, and with the fowls of heaven, and with the creeping things of the ground: and I will break the bow and the sword and the battle out of the earth, and will make them to lie down safely.
And I will betroth thee unto me for ever; yea, I will betroth thee unto me in righteousness, and in judgment, and in lovingkindness, and in mercies.
I will even betroth thee unto me in faithfulness: and thou shalt know the LORD.
And it shall come to pass in that day, I will hear, saith the LORD, I will hear the heavens, and they shall hear the earth;
And the earth shall hear the corn, and the wine, and the oil; and they shall hear Jezreel.
And I will sow her unto me in the earth; and I will have mercy upon her that had not obtained mercy; and I will say to them which were not my people, Thou art my people; and they shall say, Thou art my God. (Hosea 2:18-23)