I used to live on a sailboat in Marina Del Rey, Calif. Sometime in the 1990s, the houseboats became illegal in Marina because they had no means of propulsion, one of the requirements of moorage. The difference here, as opposed to the situation in Olympia, is that instead of evicting all of the houseboats, the existing houseboats were grandfathered in and could remain in the marina. No new houseboats could be added, but no one was evicted.
This very simple solution could be implemented in Olympia without affecting the law, or the people who will be made homeless by the enforcement of this law. If safety is a concern, perhaps putting all of the existing houseboats in one location, away from high-traffic areas would be an additional solution.
Evicting these people is not only the wrong solution, but is morally reprehensible, let alone doing it on Thanksgiving weekend. Get it together, people, and give these people a break.