If disease transmission is why we must keep hunting over bait illegal then why isn't it illegal to just feed deer period? Because you can dump out 30 metric tons of corn a year on your land if you want to. You just can't hunt over it.

Is there some weird biological force that suddenly kicks in when a man with a gun gets near a feeder that causes diseases to suddenly become a threat?

Of course not. The threat of disease is the same with supplemental feeding as it would be with hunting over that same feed. Yet I have never heard anyone even suggest that supplemental feeding be banned. Wonder why? I suspect it's because it's a highly overrated threat and not the real reason most people want to keep hunting over feeders illegal.