Caught him cheating—exposed him at our engagement party

AITA for exposing my fiance affair at our own engagement party. I never thought I would be the woman who found out the truth in front of two hundred guests. Let me start from the beginning. My name is Rachel and I was engaged to a man named Marcus for almost two years. Everyone called us the perfect couple. He was charming and successful and everyone loved him. I loved him too, or at least I thought I did. Three months before our wedding we threw a huge engagement party. My parents spent a fortune on it. My sister flew in from another country just to be there. I felt like the luckiest woman alive. That night I went looking for Marcus because it was time for our toast. I could not find him anywhere. I checked the bar. I checked the dance floor. Finally I walked toward the parking lot and saw his car with the windows fogged up. My stomach dropped instantly. I walked closer and heard a woman laughing inside. My hands were shaking as I opened the door. There he was with his assistant Jenna, half dressed, looking at me like a deer caught in headlights. I did not scream. I did not cry. Something inside me went completely cold. I closed the door calmly and walked back inside the venue. Everyone was waiting for the toast. My father handed me the microphone thinking I was about to say something sweet about my future husband. Instead I looked at every guest and asked them a simple question. I asked if anyone here believed cheating was acceptable right before a wedding. The room went silent. Then I told them exactly what I saw in that parking lot only minutes earlier. Gasps filled the room. My mother nearly fainted. Marcus came running inside, his shirt still unbuttoned, screaming that I had lost my mind. I looked him dead in the eyes and asked him to explain the lipstick on his neck. He could not say a single word. Jenna tried to sneak out the back door but my sister blocked her path and demanded she explain herself to everyone. Jenna broke down crying and admitted this had been going on for eight months. Eight months of lies while I was picking out flowers and choosing our wedding song. My whole body felt numb. Guests started leaving in shock, whispering among themselves. My father asked security to escort Marcus out of the building. He kept shouting that I embarrassed him in front of everyone, as if I was the one who ruined the night. The next morning his mother called me screaming that I humiliated her son publicly. She said I should have handled it privately like a mature adult. I told her that a man who cheats for eight months does not deserve privacy or dignity. She hung up on me immediately. My friends have been split down the middle since that night. Some say I was completely justified because he made a fool of me for months while pretending to love me. Others say I should have confronted him quietly instead of destroying his reputation at our own party. My sister keeps telling me I did the right thing and that karma finally caught up with him. My mother still will not fully speak about it because she says the whole town is now gossiping about our family. Meanwhile Marcus has been posting cryptic messages online claiming I am the villain of this story. Jenna blocked me on every platform the very next day. I have not spoken to Marcus since that night and I do not plan to. Every time I close my eyes I still see his face frozen in shock when I asked about the lipstick. Some nights I feel powerful for standing up for myself. Other nights I wonder if I should have just walked away quietly instead of making a scene in front of everyone we know. My father says I saved myself two years of misery by finding out now instead of after the wedding. I keep replaying that night over and over, wondering if there was a better way to handle discovering the ultimate betrayal. So tell me honestly, was I wrong for exposing him like that in front of everyone we love, or did he deserve every second of that humiliation.