Protestants don't believe in transubstantiation which is why we don't take Communion in Catholic churches.
Politically, I don't care if someone is Mormon.
Note: Someone mentioned "sheep stealing" earlier regarding the Mormons. I find this interesting because my neighbor is Mormon and he's been very good to invite me to his church. The elders even came by one day. In the non-Mormon church, this is considered rude and is referred to as "sheep stealing". If your neighbor is a good Baptist, you don't invite him to the Methodist church in order to get him to join your church.
Well, except for the Episcopals. Everyone is trying to steal them these days.
"Protestants don't believe in transubstantiation."
Except for Anglicans.
"Protestants don't believe in transubstantiation which is why we don't take Communion in Catholic churches. "
The precise reason you dont take Communion in a Catholic church is that you need to go through Catholic baptism and first Communion. Whatever your beliefs, you do not partake without initiation. We believe in one catholic and apostolic church, as the Nicene creed has it.
The idea that it is 'rude' to invite someone to your own church is a bizarre one to me. One can always decline such invitations.