> How does your comment fit with children being drugged and forced into prostitution?

That's already illegal. You've just made discovering it harder.

> And then adults being drugged and forced into prostitution?

Also already illegal. You've made discovering it harder.

> And then adults feeding a drug addiction?

That's actually none of your business.

> At which point of this ladder do you start to say "no, this is where we need to make it illegal"?

There's no need since you don't actually solve coerced prostitution by making it illegal.