I'm often amazed by how often crew members seem surprised when security grabs their 110g toothpaste, or when the metal detector is set off by the metal in their shoes - just like what happened yesterday
Instead of trying to teach common sense to a group of people who are neither paid for, nor often capable of, such thought, why not just have a little think about it before getting to the screening point. Hmmm, metal objects into sidepocket of bag, get your ziplock bag of <100g toiletries out, take your shoes off (and eat any large cans of tuna
).
Ok, a can of tuna being considered a LAG is stupid (as mentioned, I'd be more worried about someone trying to slash me with the lid or throwing the can at me, or maybe forcing me to eat it
), but it's not an argument you're going to win at the screening point. Just spend an extra few cents and buy 2 smaller cans.
WRT the liquid content of the tuna (not that it really matters as the LAGs regs relates to the capacity of the container, not the contents), I'm pretty sure the cans show the "drained mass" or % of tuna somewhere, so you could try to use that in your argument. Good luck!