There were two arguments presented regarding a chumming ban -
1) The shark fishers said that they didn't chum because it didn't work. To which I replied (as you say), "Then you shouldn't have a problem banning it." The Commission ultimately agreed, but, it was over the objections of FWC staff who agreed that it didn't work so why ban it? But, they were even more adamant with the following -
2) FWC staff kept making the argument that there is no proven correlation between chumming and shark bites. To which I always responded, "That's because you have never done a controlled study. So, let's try to do one. We will build two large tanks and populate them with the same sized bull sharks. Then, in one, we will put a couple of FWC staff and shark fishers, those who believe there is no correlation, and some chum. In the other, we will put FWC staff and shark fishers and no chum. Then we can see who gets attacked first." There were no takers.

I was also repeatedly insulted by a certain FWC staff member who patronizingly said that what we don't realize is that there are always sharks in the swimming areas and always used the term "anxiety" when we raised our legitimate objections. I finally had to call her out by saying, "Look, while you were studying about sharks at the Univ of Texas in Austin (far away from them), I was swimming and surfing with sharks for my entire 63 years of life. Don't tell me that I don't know sharks are always present. The intent of chumming is to invoke feeding activity. It is not a passive action." She finally abandoned that argument.