Again, I find this logic to be extremely confusing. How related is "car camping" to Seattle's homeless? Is there some implication that the majority of them have cars they sleep in? Or am I missing something there?
As for the incentive to follow basic property or drug laws, again, how does that encourage homelessness? I could understand if you argued it encourages crime, but why homelessness?
The only remaining argument is basically "this encourages already homeless people to move to Seattle", which I can see being a problem, but of a different kind. It shares certain aspects with the immigration-related problems: in both cases, it's an effect of a deeper underlying problem that acts as a root cause and should be solved.