Except that neither of the things you mention affects more people than climate change will. The estimate is that there are about 54 M people World wide suffering from alzheimer.
To put that into perspective the average altitude of Bangladesh is 9m above sea level, but the majority of the population lives in he south at about 0-1m of altitude. So there would just in Bangladesh alone be more people (let's say 50% of 160M) directly affected by climate change than alzheimer world wide. We are not even talking about the indirect effects of displacing 60M people, all the other countries and all the other effects of climate change.
Apart from that, the argument is under the false premise that we shouldnt do anything anyway because there is worse things. By that argument we should also not do something about alzheimer, because more people die of cancer.
So I question what your aim was with your argument. It was clearly using wrong facts and was under a false premise.
Just because they will below sea level doesn't mean they will all die. That's a bit ludicrous. Even more ludicrous are your nrs 4-5 meters, will get to that.
Whole of Holland is below sea level at the moment. Yet we are miraculously sitil alive.
To take it further, in a 100 years every house in Holland that's here now will still be standing.
Now certain countries don't have the skills that the Dutch have, and we should help them. But this isn't something that will come unexpected, so we have the time to do so. Half of Dubai was created out of the sea.
The worst case projection for 2100 for just sea rise is 4-5m on global average (but much higher in some areas) https://iopscience.iop.org/article/10.1088/1748-9326/acb504
To put that into perspective the average altitude of Bangladesh is 9m above sea level, but the majority of the population lives in he south at about 0-1m of altitude. So there would just in Bangladesh alone be more people (let's say 50% of 160M) directly affected by climate change than alzheimer world wide. We are not even talking about the indirect effects of displacing 60M people, all the other countries and all the other effects of climate change.
Apart from that, the argument is under the false premise that we shouldnt do anything anyway because there is worse things. By that argument we should also not do something about alzheimer, because more people die of cancer.
So I question what your aim was with your argument. It was clearly using wrong facts and was under a false premise.