I mean they're right, rising oceans will be a drop in the bucket for the majority of us. Unless we act together, human civilization will end through the combination of breakdown of global trade, mass migration due to heat and resource wars, and collapse of our food chain. Ocean levels are just one of the side effects that goes along with rising global temperatures.
Beef production in the US is already down from 30 years ago. At some point you won't be able to raise cows anywhere, less alone feed them. Corn and wheat have seen tremendous fluctuations in the past and will likely continue to fall. Imagine corn yields dropping by more than 80% in the US [1]. Of course MAGA people will probably only notice once the shelves aren't being restocked.