AITAH for calling out my friends' shitty behaviour in an argument in an attempt to defend myself?

(All fake names)

This argument happened a little over a month ago but how the whole thing played out has been stuck in my mind everyday so I'm just here to ask for judgement on my behaviour in the situation. For context, everyone in this scenario is either 16 or 17, minus one person who is 18, and the older sister of a member of the group. I was 16 when this happened - now 17.

The argument happened on a normal day, when the main instigator of the argument, John (16M) messaged in a group chat, addressing me directly, asking about a rumour that I had heard about his mum offering one of my friends (16F) cocaine at a party. (This rumour was NOT true, I knew that when the rumour was told to me). I had told this rumour to a couple of people who are close friends to John, and made sure to explicitly tell them that it was NOT true and to not tell John due to his explosive nature. I assume they were the ones who told John, as I told nobody else. When I clarified that, yes I did hear the rumour and that I did not remember who told me, he became very accusatory, demanding that I started the rumour to get his mum in legal trouble (She's single with 3 kids and works in childcare).

By this point, there were at least five people online, watching the argument take place, two of those people being people I've been friends with for a long time. One of those, Layla (17F), I've been friends with for 8 years, and last year, she got in a relationship with John, and started to grow distant with our friend group. John was in a separate friend group, which merged with ours when we started College (Age 16 in UK). I noticed that in the last couple of months, John was trying to push me and a couple of my other friends (Both 16F) away from the whole group. I used this to defend myself in the argument, stating that it "Seemed coincidental that you bring this up at the same time you're trying to push others away."

This seemed to push him over the edge, and he snapped. He said that one friend, Michelle (16F), had always been really annoying, that nobody can stand her, and that 'everybody thinks it, they're all just too scared to say anything', and that another friend, Charlie (16F), just 'talks shit' and takes up too much space. Others in the group started to add onto those comments, defending what John was saying and backing me into a corner.

At this point, I'm just disgusted by the way John is speaking about my friends, and Layla is doing nothing to defend any of us, who have been friends with her for over 8 years each, so I leave the group chat and block everybody involved, including Layla which really hurt me to do, except for the friends I tried to defend. I will admit what I did after was slightly immature - I posted a couple private Instagram stories basically calling out the shitty situation and clarifying that I don't see how I am in the wrong for calling out their awful behaviour. I was met with some angry paragraphs that I ignored, blocked and moved on from.

So, people of Reddit... AITAH for calling out my EX-friends' shitty behaviour in an attempt to defend myself in an 'unwinnable' argument?