It's sort of like the people who react to robotics with concerns that the robots will go rogue and turn on their creators. Yeah, this is like a 90% probability event in movies, but that does not make it a reasonable thing to worry about in the real world.
Yeah, of course we should carefully think through the consequences before acting. That's what is happening. But if the mosquito experts say the ecological impact is likely to be negligible, then it probably will be. These guys are experts. Species go extinct all the time, and life goes on because it's pretty robust.
I'm not saying scientists are all knowing and can foresee all side effects, though I suspect if they are willing to state a view like that with confidence, they won't be far off. What I'm saying is the ZOMG BIRDS EAT MOSQUITOS and WHAT IF WE INFECT OURSELVES AND GET WIPED OUT talk is a little silly. Cool it there, Spielberg. ;)