The known bad is hundreds of thousands of people dying
every year. It's pretty hard to conceive of how a
laboratory tested solution which kills/slows down mosquitoes could be any worse than that, particularly when all sorts of genetic modifications are occurring
by the billions in nature every single day without
any testing/verification.
You know what would turn around everyone's attitude in about 7 days flat (probably fewer) - have those hundreds of thousands of people dying a year be white, rich, Americans. Every conceivable solution to wipe out the mosquitos would be developed, and rolled out with zero debate (and I mean zero - there wouldn't be a single naysayer of any merit)