Well, the country is reliant on tourism.
But bad apples are everywhere, I think such people need to be held against their will until they are no longer dangerous to others.
That's immoral, unethical and insane:
Not specifically talking about these supposed two French tourists. Iceland obviously has had domestic cases of individuals who believe the virus to be a hoax, and thus decided not to quarantine after being tested positive.
These individuals were, according to memory, held against their will during the remainder of their quarantine and fined.