It is not considered retaliation legally. Whistleblowers, people who complain about bad treatment or sexual harassments or illegal practices in fact do have bigger problems to get hired.

If the whistle-blower acted in concert with even one other coworker, and made it clear to all that their actions were concerted, and the whistleblowing was itself legal (e.g. not divulging a trade secret for the sole purpose or harming the employer), then the refusal to hire such a worker could be a violation of 8(a)1 of the National Labor Relations Act.

But this would be hard to demonstrate in most circumstances.

I do not think the whistleblower has any right to legal protection outside their previous company. Which means they may have to work there for life.

It depends. Almost all whistleblower laws are statutory and vary by jurisdiction and subject. Therefore, it just depends on how the statute is phrased - and almost never did the legislature even consider this (or other questions like “What if the whistleblower was wrong?”) So, the results tend to vary considerably.