I don't think keeping sex work safe was really part of the point. If anything, making things unsafe for prostitutes was.

When your viewpoint is centered on the law and nothing else (as is the case with the people shutting down myRedBook.com), it's easy to see the criminals as a sort of enemy, rather than a human population. From there, it becomes really easy to justify doing things like this in the name of hurting the enemy. It's the same mental glitch that enables warfare and genocide, just on a much smaller scale, and more carefully directed.

Also, I'm pretty convinced that the human trafficking problem is a red herring when you think about the money involved. The US budget for fighting human trafficking is $50 million per year (For reference, the war on drugs costs more than $50 BILLION per year). Prostitution enforcement helps with human trafficking mostly by happy accident (they're correlated, so traffickers are likely to get caught in the same net), but if the money taken from that was applied to solving the problem directly, it would make a much bigger impact. One of the biggest problems in enforcement right now is that everyone involved with the industry is seen as that sort of enemy, so trafficked people can't get help for fear of arrest. Legalizing prostitution would allow trafficked people to get help without fear of reprocussions, and put a massive dent in the industry.

I don't see prostitution and drugs being leagalized any time soon though, because a pillar of the current govenrment's legitimacy is the promise that they will spare no expense in protecting us from our fears. Foreign powers like ISIS and Russia are OK for that, but they're so removed from our daily experience that it's hard to make people really scared of them. Pimps and drug dealers make for much better domestic threats, even if the problem is easily solvable by a paradigm shift in the way we approach them.