There are ALL KINDS of food regulations, and this is just another one. It's not like they're breaking new Constitutional ground here.
It's unreasonable to think that people are able to know all about every ingredient in every food. Suppose you buy a food item, and on the label is "dichromium sulfide" (I made that up). Is that safe to give your kids? Who knows? That's why we have an FDA, to regulate the foods that are put into the open market so that consumers can have some confidence that they aren't being poisoned. Turns out trans-fats ARE poison, and worse, the only reason to use them is that it's cheaper for food manufacturers. It's not like they're banning anything that people are clamoring for - in fact, most people have no idea what trans fats are or how dangerous they are. We're not talking about just "fat" here, but a man-made fatty product for which the body is essentially unprepared. And it's in your dinner tonight! Maybe! You don't know, since ingredient lists and nutrition labels are not offered at most restaurants.
Personally, I'd like to be able to go to a restaurant, and not demand ingredient lists and nutrition labels on every item to make sure I'm not being poisoned.
I'm a social libertarian, but you have to balance public safety against personal choice, and in this case I'm not sure who wants trans-fats, except food manufacturers looking to save a few pennies. They're just a menace, and one for which there are abundant, safe alternatives. It doesn't have to be healthy, but your dinner shouldn't be poison!
Capslock