What to do with threats of blacklisting?
You went to the administrative person. That was your error and the core issue. 

Allow me to give an example from the other side in which this happened:

While I was at another institute, I was asked to take over a lab for another person. The lab hosted a guest cohort from another country so the university needed someone with content knowledge and dual language fluency on short notice. So I was asked if I could take over the lab for a week. 

Suffice to say, I did not know that there were particular rules for this lab. Some were obvious (like not leaving equipment plugged in) but I was a little overwhelmed with taking over a course last minute. Further, my work is primarily computational rather than lab focused so the reflex nature of lab rules was not there for me. 

After a few nights, the lab manager came in and saw the lab after I had left it. Equipment was left out and plugged in. All a very big mistake on my part. The way she responded was where things got messy. 

In hindsight, a more measured response would have been talking to me or even the lab's PI to find out what was going; even going to the department head. Instead she went to the Dean. She did not know the situation with the lab and the dean didnt, but as soon as it went to the dean, the situation became "administrative". Funds were threatened and it ended with me having to write a formal apology to the department head and the lab manager with everyone CCed on the email.  Everyone was aware the situation and most parties were mainly pleased that I was willing to write the apology so the "administrative" side of the situation could go away and we could fix things in house. (I ended up just getting an assistant who was a little more lab savvy). The department head came by and gave me a sympathetic pat on the back. 

Was I wrong, certainly. But it was likely an issue that could have been dealt with "in house". 

So, what was the end result of going to the administration rather than keeping things in house?  At one end, awkward elevator rides when the lab manager and I crossed paths. She found out the situation, and to find out, she didnt even know I was in the lab. I heard she thought it was an undergraduate group. On the other end, it did leave some lasting trust issues and undermined what had been before a very good working relationship between two labs. But I think that things have smoothed out since that happened. 

In other words, once you go to the administration, the situation becomes administrative.