As far as I can tell the Icon of the Seas is basically fine; even on the environmental front (important!) I see no reason to believe it's worse per passenger than other ships.

A lot of opposition to it feels like elite snobbery against middle / upper-middle-class people.

Any good anti-Icon arguments I'm missing?

Here's an article I found that examines the various environmental claims. I wish it had dug a bit deeper into some of it, but it makes a lot of interesting points, like how the fancy new scrubbers mostly just turn air pollution into water pollution, etc.

Here's an article I found that examines the various environmental claims. I wish it had dug a bit deeper into some of it, but it makes a lot of interesting points, like how the fancy new scrubbers mostly just turn air pollution into water pollution, etc.
https://www.greenmatters.com/travel/icon-of-the-seas-comparison