It is a comparison to something of a lesser status. No one is of lesser status than clergy in the eyes of God.
OK, thanks, I get that (I think.)
But it also seems to me that it's a way of distinguishing one category of roles of service, from another.
It's as if I were to say,"Don't call that MD a doctor, we're all doctors, we all have primary responsibility for our own health and wellness."
Or "The words 'Mother' and 'Father' are offensive because the imply the other people in the family are of lesser status."
To be offended by "lay person" implies ---- if I am understanding you correctly--- a resentment of any distinct role or status. And yet St Paul says distinctions in the community of believers are instituted by God:
1 Cor 28-31
And God has appointed in the church
first apostles, second prophets, third teachers;
then deeds of power, then gifts of healing, forms of assistance,
forms of leadership, various kinds of tongues.Are all apostles? Are all prophets?
Are all teachers? Do all work miracles?
Do all possess gifts of healing
Do all speak in tongues? Do all interpret?But strive for the greater gifts.
And I will show you a still more excellent way.
And then he talks about the excellent way of love. All these people of different roles, different status, they don't worry about status or resent status: they love one another!