You don't see this as turning "innocent until proven guilty" on it's head? That asking them to self incriminate themselves doesn't violate a Constitutional precept?
They can ask, but those Citizens have a Right to tell them to get probable cause or go pound sand...
If they were to ask me to come in and clear my gun the first person I call is my lawyer. I would urge anyone to do the same. But, their asking isn’t an issue for me.