They moved here in the first place to be allowed to practice their religion how they see fit. They were pretty much driven out of Europe, along with e.g. the Quakers and Mennonites
Any good poll accounts for people who won't pick up the phone. Otherwise you might as well not poll.
As for the 4%, that's why I said it's a bigger number than I'd have picked. There is probably a perfectly reasonable answer as to why it is 4%. I just gave you one example but it's easy to tink of a few other scenario's: poverty, lack of internet availability in rural areas, the exact wording of the polling questions, etc. It's not my poll.