Can “an over-concentration on the ‘objectivity’ of baptism . . . lead to a . . . casual or careless approach to actual Christian obligations”? Wright says so ( Paul and the Faithfulness of God , 963).
But that assumes that what baptism “objectively” says and does is simply, “You’re in.”
And that’s not what baptism says and does. It says “you died and have been raised; therefore kill sin and live to God.” Baptism objectively declares something to be true, objectively makes something true, objectively promises, objectively demands.
It’s not over-concentration on objectivity that’s the problem. If there is a problem, it’s bad baptismal theology.