Honestly, the first one looks like the only valid reason. But is this about credits and stealing or getting mad because of inevitable technical progress that can make their work faster and cheaper? So there's a question: if a certain AI was trained on the arts, whose artists gave their full consent, would it be okay for you?
You said yourself that 'Many people were using it as...'. People can use anything to make harmful content. It's like hating knives because of murderers or existence of cameras for filming inappropriate things.
Water consumption and carbon footprint... Well, almost everything made by humanity has a negative impact on the environment. Should we cancel people for watching Youtube and Netflix then? Or even real musicians mentioned in your reply that use Spotify? Their data centers also create big environmental problems.
Cognitive abilities. Depends on people. For instance, before AI I read my lecture notes or textbooks, tried to understand a certain problem and ended up frustrated because everything wasn't explained clearly and I had to google it for hours just to find another tricky explanation. Now I can upload the whole textbook or paper written by very smart people, who study their subject for a lifetime and use their very smart scientific language, where they just say 'as you already know, ...'. I can ask AI to explain it to me in understandable words and it really works! As for essays and book reports, I've always thought they are extremely outdated, like the whole university concept. I don't know about other countries, but in mine students used to download texts from Google, then just read them at the seminars a few times and get a good mark. Now they do the same thing with AI and I think AI just made this problem more obvious.
Companionship. People don't like hearing about other people's problems. AI never gets tired of your problems and that simply reveals the dark side of human psychology.
About the boys, yes, I will point the finger at the parents. And maybe it's not only their fault, sometimes parents can't control things like their child's emotional state or social circles. Minors can find destructive content anywhere: forums, chats, friends, AI, darknet. That's the question about access control.
AI is just an instrument.
I think it's ridiculous to accuse all AI users of global problems.