Labeling someone a cheater

Let me start by saying cheating is wrong and I am in no way denying that. I commented on another post and saw so many people posting ONCE A CHEATER ALWAYS A CHEATER. I myself cheated in a previous relationship and I am not downplaying my cheating. I should have left when I was unhappy, not cheated. Saying that, he was an alcoholic, abused prescription drugs, was verbally and at times physically abusive, he refused to work a job and ran up tons of debt in my name. We were together 7 years, I started seeing someone 6 years in. Now I am with someone else. We have been together 4 years and have kids. I would never cheat on him and I know that deep in my heart. I think people change and circumstances affect situations. I think if you cheat on someone you will cheat on THAT PERSON again, but not everyone your with. I think it's an unfair label. Give your opinion.