You didn’t properly secure your account and as a consequence people who added you had to look at pornographic pictures. Facebook had to ban your account. I don’t see how you’re the one wronged.
Banning on Facebook is justifiable from every angle but not exactly on Instagram.
There is no universal Meta Account (like google account, apple ID). There are two different accounts for two different services.
Illegal/Unethical banning of OP's account on Instagram.
I was the one wronged, 16 years on the platform, changed my passwords ever 3-6 months and this so the first time my account got hacked.