I think a ton of people were REALLY misinformed about how much water AI data centers use. I know I was at one point.
Now there may be people pushing that narrative still on purpose because it clearly works. But I don’t think the average person who uses that talking point is doing anything other than expressing a concern based on the (terrible) information they got somewhere.
There's a reason certain types of misinformation become popular and others fizzle. The environmental concerns around AI are starting from the goal 'disliking AI' and going in search of a reason for many people. The environment is a convenient reason because it links to an existing left-wing cause & doesn't require conceding the frame of AI rapidly becoming extremely capable (scary! don't like to think about that!) so it's all comfort and outrage without stakes.
Beef consumption wasn't a problem in the 70s either.