I was let go from my job as a Site Manager in May.

I have always been very successful in my roles and feel that I had made significant progress in this facility however, there was still much more to work on. I wasn't given a real reason, just it wasn't working out. This is after earlier in the week I found that we were doing something unethical, and potentially unsafe to consumers using expired material and I publicly stated it was not something that I condoned, and it would not happen again. This was on a team's meeting with our corporate team and sales. I suspect that it was something that may have been a normal event. I have had several very successful interviews since. Was told I was the most qualified person that applied in a 3rd interview that was with the executive team and another interview for another position with the Plant Manager where he told me to take the safety glasses and use them on my first day. After those interviews, I had multiple former co-workers view my Linked In profile it was hours after the interview. I suspect that I am being blackballed when potential employers call my previous employer. Any ideas on how to handle? I have requested feedback from the potential employers after receiving the rejection. I am strongly considering contacting an employment lawyer but realize it would be difficult to prove.