But I don't think sharks are going to be the -only- part of the choice. So if say, the touristry minster of a state in Australia killed 3,000 sharks; but I knew there were still bull sharks in Playa del Carmen that attacked a person at the beach; well, I still wouldn't go dive in Australia because it is 'safe'. Because 1) I would not want to support the decimation of a species and 2) it's crazy expensive to get to Australia. I'd still dive in Mexico.
In this scenario, all things were not equal. So let's say two destinations cost the same, and all else was equal. As a tourist, I would not give my money to a region that culled sharks. I don't care if it makes me statistically safer; statistically, I was already very safe and the world wide food chain hasn't been interupted, not to mention the life of so many animals.
Yes, all is not equal. But not everyone lives close to Mexico and far away from Australia. Yes, sharks are not the only thing. But for example, a co-worker recently went to Hawaii, relax some at the beach and swim and snorkel. She was very afraid after she read the news about a shark attacking a German woman (who sadly did not survive). From Germany, it's like 24 hours to Hawaii. Same time you can be in Australia, or anywhere else in SE-Asia (or in Mexico). (She went anyways, and she did snorkel and enjoyed it very much.)
There are people who read up on sharks, data and statistics etc., but there are also people who just do not care and just want to enjoy their vacation. For them, it's probably the obvious choice to pick a country that is in their mind "safe". And I fear they are the majority.
If it's just for diving, for me there are still plenty of spots in SE Asia left that I want to dive, so for diving alone I'd not pick Australia (not because of the sharks, but it's expensive and far for me too), no matter if they cull or not. I would pick Australia though to dive with a friend, no matter if they cull or not. As you said, all things are not equal when picking a dive destination.
But I agree with you, if all things were equal apart of the culling, I'd pick the country that doesn't cull.
(By the way, I'm not trying to defend the culling, but I can see why some people are in favor of the culling and think it is the way to go.)