"Bad" according to whom?
Sure there are plenty of internet conspiracy theorists who make unsubstantiatd claims about Splenda and other sweeteners, and there are many times more people who take these claims as fact, but I have yet to see anything about how the quantities consumed by people through normal use (not 10 kilos worth per day) are hazardous.
Have you ever known of anyone to suffer from using an artificial sweetener? I haven't and I've been around people who drink diet sodas in higher quantities than most of drink water.
Don't worry about the boogie men.