Sorry you had a bad experience; mine have been just the opposite. I haven't had anything at all confiscated at the screening counter in numerous trips to Cozumel over the past several years. I understand that you are irritated and probably just venting, but I certainly wouldn't let something like this dictate where I would or would not go to dive.I can attest to this not being true.
For the second time returning from Cozumel they decided to take random stuff. First time was aset of Allen Keys on the basis that tools are not allowed, regardless of the fact that the cases with forbiden items doesn't say anything of the sort. Last night out of the whole carryon that had flashlights, camera and cases, chargers, they decided that the 2 small pieces of lead, not bigger than 5x5 cms we use on the camera case as weights, were not allowed because they are heavy objects. Seriously? but the two heavy metal flashlights were not heavy objects and last time those small weights were not a problem.
So my conclusion is that they have no damn clue what they're doing, its all how the wind blows. Unfortunately it is alienating people, and personally, just becuse of this two bad experiences Cozumel is off my future travel list. There is a very good reason for the stuff I keep in my carryon, if some a** decides to go on a power trip and make his own rules and take my stuff for no reason I will not return.
So to future travellers to Cozumel, anything is fair game and can be confiscated out of your carryon.
Tools, no matter how difficult it would be to use them to cause an in flight problem, are subject to confiscation, so I don't put any in carry on, even tiny eyeglass screwdrivers. Likewise, batteries; I use a lot of alkalines of all sizes and I leave any that I have left over with the dive shop, though they have never said a word about the ones in my video bag. Liquids are right out, of course.
It's really not that hard to avoid problems, and getting into an argument with the folks at the screening desk won't accomplish anything besides getting yourself worked up. Good luck next time, if there is one.