Work related drama- don't know how to handle it.

About one year ago, I got fired from my job.
My boss didn't tell me why when I asked him, but did tell me it "wasn't work related." He told me that he "couldn't trust me anymore."
Leading up to getting fired, I had been looking for different jobs for several months. I felt like my job was unstable because I made the mistake of dating someone at work who was insane. 
Probably two months after I stopped dating the person is when I got fired.
The person I dated at work was crazy. He would drive past my house and send me harassing text messages and spread rumors about me at work. 
I had a feeling that me ending the "relationship" had something to do with why I got fired, but I'm starting to really think it's true after today.
Today, me and my new significant other (now my spouse) are at a conference and the people from my old work, including the person I used to date, are also here. Usually they all are super friendly to my significant other and would want to chat, but they are all acting very passive aggressive by ignoring us. It's so childish. They usually even at least acknowledge my presence, but they are all literally pretending to not see us when we are feet away. It's ridiculous. This is the first time that I've been in this situation since getting fired last year. 
 I don't know what to do. It makes me so upset that my significant other has to get caught up in this unnecessary drama.
 To make matters even worse, the guy I used to date stared at me during the entire conference (which was several hours long).