This presumes that everyone who builds in coastal areas is "gormless" and deserves hardship. Millions of people live on islands and they don't get a choice where they build. Several Polynesian countries will disappear by the end of the decade. Are they "gormless"?
"The article makes it sound like", which I used to emphasize the seeming misunderstanding that the author seems to have. Insurers aren't stupid. I don't think the author is stupid either; I think they're just not a SME. And unless you have credentials, neither are you or anyone else here. We have to be better at listening to the experts who dedicate their lives to this stuff, and we need to fund them whatever they need to do their work.
This seems based on outdated science to me. The world isn't just "getting hotter", the overall climate is changing due solely to human influence. The article makes it sound like insurers believe houses will start spontaneously combusting. What they should really worry about is desertification in populated areas and flooding along the coasts, and the inevitable humanitarian crisis and necessary social restructuring that those will require. We can't leave this to insurers - we need strong cooperation between governments and academia to plot a better course into our brave new world.
I'm not sure what you call this fallacy. It's not really whataboutism because you're not equivocating against another argument, but instead you just discard it and push forward on the path that you've chosen for this interaction. I guess it's begging the question. I can see that this would be a powerful technique in a more open forum, or against an uninformed audience, because by pushing like this you imply that you are so correct that no other argument need even be heard. What is the "win condition" here for you? Do you have any other examples of your work, or do you cycle out soon?