This is a pretty stupid argument if you think about it.
Something has to be The Worst Thing In The World. For every issue other than that single one, someone can raise the stupid argument "Why do you care? You should be caring about The Worst Thing In The World! Ha ha, you are a hypocrite and I just caught you!".
The answer is simply that there are lots of bad things in the world, we can't all be working to fix all of them, and fixing the second-worst thing should not wait on fixing the first-worst thing. Trying to fix any problem is laudable, and you don't lose credit just because there is some other problem you could be fixing.
On the bright side, you've obviously solved the problems of AIDS, Middle East unrest the common cold because you have time to post here. That's good news at least. I'm glad the only problem left in the world for you to solve is someone being wrong right on the internet.