First I want to say thanks for answering to a few-days old comment, I was wondering whether anyone uses the fediverse more like a forum. That's kind of nice, knowing that the comments are not just shouted into the void and forgotten :) Second I want to say sorry for my answer - you stirred up a hornets' nest :D

Even when ignoring ANN, I could list way too many arguments why data centers suck, and already sucked before "AI". But before I get into that, let's start from the top - buckle up.

Water use is not really a problem of data centers - they can't require more cooling than thermal power plants generating their electricity, and I have yet to hear someone complain about the water consumption of thermal power plants. (That's the TL;DR of a way too long comment I put way too much time into, if you want more info and sources)

And as for your proposal of requiring data centers to produce 110% of their own energy with renewables, I restate my earlier sentiment:

Even if the data centers would cover their own energy usage with green energy, that’s energy that could go towards decarbonizing all the other stuff we “need” to do.

As long as our energy requirements are not completely met by renewable energies it won't help if you require data centers to produce 200% of their energy. It's not like we have spare solar panels or wind turbines lying around that would not be put to use if there were no data centers. You basically already have that idea with

Or they could just turn off the computers and sell the electricity.

so yeah... building solar parks or wind turbines just without the data centers.

when the bubble collapses, we get a bunch of cheap, green compute that hobbyists like Myself can use for our little websites.

That would be nice indeed, but AI data center hardware is not really suited for hosting websites. Unless you can host websites on GPUs or TPUs you will have a lot of "green compute" e-waste. Even the bare-bone servers without the GPUs/TPUs are way too overpowered to host "little websites". As far as I'm aware, serving websites does not need too much compute power. It's more about storage and bandwidth, depending on the kind of website you host. For ideas on how to actually sustainably host websites, see e.g. https://solar.lowtechmagazine.com/about/the-solar-website - this is all just to say that "green compute" is a more complex topic. It's not just about getting your energy from renewables. The 512KB Club also comes to mind. (This is a first step to respond to your "Most of the internet runs on [data centers]." - I don't even want to know how much bandwidth and energy is wasted on ads and surveillance. That's also part of the data centers that run the internet.)

So using those AI servers to host websites would just be wasting energy and resources. Granted, those resources are already wasted, which would be my other criticism here - even if you repurpose the hardware used in the data centers, I would not dare call that "green". Producing those chips requires a huge amount of energy, so they already have a lot of embodied CO2. Always getting the newest hardware just for the sake of it is not "green". Keep your computers alive for as long as is reasonable!

Now to finally get to

Data centers are actually pretty cool when they’re not being used for ANN tech. Most of the internet runs on them.

As I hinted at earlier, I'd say it strongly depends on what the data centers are used for. "Internet" is a broad term, and there are many data centers that aren't used to host websites. The Oil and Gas industry used to (and actually still does) operate some of the biggest supercomputers just to find new oil fields. I wouldn't call that useful. For some examples on how the tech industry sucks up to oil and gas companies, see one of my other comments. It mostly also works the other way around - search for the name of your favourite "multinational energy company" and a combination of "data center" or "supercomputer" and you'll most likely find something.

And it doesn't stop there, that's just the first example on my mind. There is a good reason some CPUs or GPUs have been classified as dual-use by the USA. Data centers are used for all kinds of atrocities. Even the ones that are used to run the internet, I'm wondering which of those are a benefit to society.

Sorry this got so long, I can't even blame you if you didn't read it all. I think I just had to get all of this out somewhere.