So... who all here is familiar with the term "Opportunistic Carnivore?"

Deer eat baby bunnies!

Also, just because something is an herbivore doesn't mean it's not dangerous. Look at Hippos, they will mess you up if you get close to them.

This is very true. Some of the most aggressive animals are herbivores, because carnivores always have to balance their aggression with hunting or scavenging so they don't typically do anything more than "scare off" something bothering them if they aren't hungry

Ah, but a brontosaur probably just does bludgeoning damage. And if Luffy isn't immune, he's pretty close. So while it's quite sensible if it tried to stomp him or drop him, Luffy in particular is probably perfectly safe. Though everyone else might not be in that same boat since something that big is dangerous whether or not it intends to hurt you.

These dinosaurs could (in theory) do enough bludgeoning damage to injure even Luffy... I literally don't know Pathfinder/D&D 3.5. XD From various other systems, there are enough variables I'd still be leery of testing the limits. Luke wouldn't, of course! :D

Spoiler Warning from the actual manga/show from this chapter/episode:

Luffy does get eaten, and that is in-line with real world herbivore behavior. Besides the one's that do eat meat if given the opportunity, Luffy is so small he just counts as a pest, like a very large insect bothering a cow or something. So, even if Luffy was completely safe from bludgeoning damage, he'd be facing potential suffocation and acid damage in the stomach. Though - Spoiler for a future arc - based on how Oda has handled other giant animals, Luffy would have sufficient time to find a way out before those were real concerns.

With bodies that big, suropods can't afford any more brains than it takes to just constantly eat; so Luffy can take solace in there not being an ounce of malice if it does try to hurt him.