I thought a big part of the opposition to data centers was due to the massive spike in electricity costs, or even loss of availability in getting power, for regular people while the data center gets a deal. If they actually paid for the new power generation, I doubt there would be much backlash.

That it's likely to be used to mine your personal data and be used to create AI slop in exchange for more global warming are just reasons to hate it more, but I think it's not the primary hate point.

Well, they're already bidding up generating capacity contracts for upcoming years. The net effect is raising everyone's electric bills today for a data center that might not even get built in the future.

The real kick in the pants is the ever present danger that you'll end up with a data-center that generates its own power on site, using turbo-generators running 24/7/365 because the grid and generation doesn't have anywhere near the required slack (aka resilience, aka redundancy) to take on hundreds of gigawatts of new base load. In addition to the noise, you also get particulates and pollution.

If they do manage to avoid local generation, you're still left with the noise of cooling systems, and the waste heat island.