Scripture-first response
“Oneness has no room for real Father-Son distinction.”
The distinction is real: God is eternal Spirit, and the Son is the genuine human life God assumed. The Father dwells in the Son, who obeys, suffers, dies, rises, and mediates.
What the objection is claiming
Any non-Trinitarian account is assumed to deny relationship, incarnation, or mediation.
John 14:10
Believest thou not that I am in the Father, and the Father in me? the words that I speak unto you I speak not of myself: but the Father that dwelleth in me, he doeth the works.Open full referenceJesus explains the revelation: the Father dwells in Him and performs the works.
How the passages answer it
Biblical distinction need not be a distinction between divine beings. Incarnation introduces a true human subject and mission in which God is revealed. The Father-Son relation is therefore real and saving while the divine identity remains indivisibly one.