Not every person who wears a yarmulke is a Rabbi, and kufis are as common as baseball caps in parts of Africa, and they have no religious significance to many who wear them. Hijabs are, likewise, not worn by someone who has taken a vow to serve their religion. Wearers of hijabs are not representatives of The Church, and are not analogous to Nuns. The bold is not true in that sense.
Holding this sign, they are explicitly there to support trump, and wearing those Habits they are specifically representing the Church.
There's a clear difference between being a member of a religious community and being a representative of that community, much like a person can be a member of a political party but not be that party's representative.
A quick google shows there were quite a few Nuns vocally supporting trump through the campaign. That's troubling.