From Reason's perspective, the ironic part is that, even if Backpage is guilty, this is still a great case study for legalizing and regulating sex work. Even from a libertarian agenda, this is kind of an own goal for them.

The fact that any and all prostitution is illegal in the United States (outside of certain counties in Nevada in certain regulated and licensed brothels) means that running a service like Backpage requires people who are, ipso facto, willing to be accessories to criminal activity. One should not be surprised when it turns out that such people end up being accessories to even more criminal activity than originally bargained for!

If you outlaw online classified ads for sex workers, only outlaws will manage online classified ads for sex workers.