No one can seem to point to any real harm [from climate change], certainly not currently.So that's silly, as well as completely missing the point that you can attribute events to climate change if you conduct the thought experiment of removing all the increased greenhouse gases and ocean heat. It also shows the real motivation for lukewarmers tricking themselves on the issue of attributing severe events - they think that if you can't attribute any one injury with certainty to climate change, then no one anywhere has been injured by climate change.
A general solution to this is to educate people about statistics and probability, but a more specific response might be to look at the 6000-plus deaths from Typhoon Haiyan. Wiki says most of the damage and loss of life was from a storm surge of up to 19 feet. In that part of the world, sea level rise to date is even worse than normal. Let's say it's one foot, although you could plug in another number.
Now depending on how good the original data was or how well it could be reconstructed, you could figure out the death rate in an area at a certain level above sea level that was hit by a surge, compare it to death rates a foot higher and a foot lower in sea level and figure out the incremental mortality from sea level rise. For example an area 16 feet above sea level with a 19 foot surge might experiences one death while a similarly-dense bordering area 15 feet above sea level experiences 10 deaths, 14 feet elevation 30 deaths, and 13 feet with 60 deaths. Sea level rise is responsible for 9 deaths at 15 feet, 20 deaths at 14 feet, and 30 deaths at 13 feet. You could do the same calculation with property damage. My guess is the numbers keep going up until you reach areas where everything was flattened.
For people, an additional complication is that many evacuated, so the actual population density when the storm hit probably wasn't what a survey showed in normal times. Maybe you can account for this. I'd guess though that the lowest areas were the most likely to evacuate, so not accounting for evacuations would underestimate the effect of sea level rise.
And Haiyan was just one event.