Using other people's data for dissertation: ethical or not? It was recently shared with me that a professor in my department (and if anyone saw my question about the verbally abusive ex-advisor...yeah, same guy) offered one of his PhD students his own corpus of data for writing her dissertation, and apparently made this offer in response to her deciding to quit the PhD program. As I understand it, she accepted this offer and decided to stay in the PhD program because of it; I also believe that this corpus -while used in a number of publications - as a whole is not publicly available or anything. 

Because I am admittedly biased (see the aforementioned question for context) against this professor, I don't entirely trust my judgement. Is it just me, or is this a ridiculously unethical offer? 

Next question, if it is unethical, do I say anything about it to anyone? The person who told me did so in confidence, and I don't want to betray that. I'm hoping he reports it (he said he's thinking of talking to the graduate director in our department about it, as he thinks it's shady too) but if he doesn't - should I say something or just let it go? Because I already have a bad relationship with this professor and have complained about him, I feel like me complaining yet again about something else will just make me look bad and not be taken seriously, not to mention there is the whole matter of this not being any of my business.

My heart and soul are all riled up because I just want to see this professor be held accountable for something (I'm pretty sure he's going to get away with how he treated me. See linked post), but my self-interested brain is telling me to let it go and stay out of it. Thoughts?
Unless the student claims that they collects the data himself/herself. I do not see any scientific misconduct in using other people's data with their permission. 

Of course collecting good data is a contribution. However, even if the student collects data themselves, I would be very surprised if that is more than 30% of the contribution in their thesis.

TL;DR: No big deal. That might be a bad professor, but it doesn't mean everything he does is wrong.