I really enjoyed Erdude's schooling, on style points alone.
In terms of substance, I'm not endorsing blacklisting people who go to work for the ME3, especially since it might be more intelligent to hire them. I don't think there would be anything illegal or immoral about hiring a competitor's pilots.
As far as blacklisting goes, the abuses by the respective carriers have not been catalogued until now, and may yet be remedied/mitigated. A guy who went there before, was going for a better job. A guy who goes there in the future, assuming the allegations are validated AND not remedied, would be deliberately going to work for a company that cheats US pilot interests. Like a scab. At that point, you could reassess any official position, and blacklist if warranted.
First, we need the respective airlines and governments to actually address the problem.