So I am writing this a few hours after it happened and I feel like shit.

For some context, I (M24) am visiting my mom and my step-dad, they live in a different country than I do so I don't get to see them often. I have a close relationship with both of them, my mom and my dad divorsed when I was young and my dad died when I was 14 so for most of my life that I can remember my step-dad has been like a father to me, he helped me through when I was mourning my dad, he has generally been good by me.

Despite this, he has his issues, he has caused a lot of turmoil in our family due to his issues with drugs and alchohol. During this time my mom went through a lot, he would often dissapear for days at a time with no explanation, spend sigificant amounts of money when we were struggling, and lie to us all about what was happening, and although since he has been sober for over two years, this has still caused a lot of rifts in our family as he refuses to come clean about his issues to his side of the family (with the exception of his mom) and so most of them hate my mom and think she treated him unfairly during that period for no reason. Because of all of this, I do have my issues with my step-dad, but I talk to him 1-on-1 about this fairly often and he has been receptive to what I say for the most part.

Regardless, the argument that just broke out is because my mom is having some health issues at the moment, for a while we were very worried because we thought it might be cancer (my dad, and both grandparents on his side died of cancer so it is a very worrying thing for my family), when she found out there was a possibility, my step-dad was not in the country as he was visiting family back where I live and when my mom called him for support he declined the call and told her he was busy.

This obviously caused a lot of issues, my mom felt like she was being abandoned when she was at her worst, and I agree with her, since I got here this argument has been going on for a couple of days and I've been trying to stay out of the way and not get involved. Whilst I think my mom is right to be upset, I also don't feel it would be helpful for me to get involved in a heated argument and to instead try and talk to them both individually and see if I can get my step-dad to understand why my mom is so upset.

All this leads up to a couple hours ago, I was sitting in the lounge watching TV when my mom walked in and said she wanted my opinion on something, I did not know I would be walking into the middle of an argument. She asked me to give my take on everything that is happening and I tried to be as calm and diplomatic as possible at first to get my step-dad to understand by as everything began to escalate I got upset and I told him that my mom should have left him a long time ago.

He looked crushed by this, and whilst I still think my mom is in the right and he fucked up, I also feel awful because despite his issues he has always been there for me and treated me as if I am his own son. I feel like I should have just set a boundry and said I won't get involved because I feel as if me joining in has done nothing but make things worse.

So, AITAH?