Human trafficking is very complex subject, and the response to human trafficking is even more complex. It is the very complexity that makes discussing Prop 35 so difficult, especially in limited news bites: to really understand the impacts of Prop 35 (whether you consider them positive or negative), you must first understand the complexity of human trafficking and the work of anti-trafficking experts. Voting in favor of Prop 35 simply because, for example, it raises prison sentencing and this will reduce the incident of trafficking (in the opinion of Prop 35 supporters) does an injustice to both the victims, and those who assist victims. If you really care about this issue, there are opportunities to learn more.
Also, for some excellent background on the creation of anti-trafficking law in California, read this article from the Pacific Standard written by three experts in anti-trafficking law, including Kathleen Kim (author of a post on this blog) and Cindy Liou (who will be on the Stanford panel).
We owe it to the victims of slavery to really understand this complex dynamic, and to vote with knowledge as well as passion.