Yes, in a loose sense we are, but there is a reason there are Protestants and Catholics.  There is a reason there are Presbyterians.  Modern liberals like to pretend the differences do not matter.  They like to minimize the differences.  The differences DO matter.  They are not insignificant.  

The whole point of Protestants vs. Catholics is that we Catholics do things Protestants do not like and visa-versa.  A Protestant telling Catholics what they should or should not believe or do in their theology and Faith is analogous to me going into your house and telling you "You should not ask me to take off my shoes before I enter, that is offensive.  You should change your practice."  Your house, your rules!  If I don't like it, I can leave and go to MY house where I have MY rules! 

Protestants and Catholics might loosely be brothers and sisters, but that does not give Protestants the right to tell Catholics what they should or should believe or do in their Faith life or churches.