@KevinB I agree. I prefer everyone to be outside of the animals enclosures (except for example free flight aviaries/green houses) and not interact with the animals on this level. People were walking around with the lemurs, "forcingly" holding them infront of their kids and things like that.
@Daniel Sörensen Wow, that is pretty bad - exactly the kind of thing you don't want to see as a zoo. That is very worrisome in terms of possible human or animal injury.
It seems to me that walk-through exhibits with primates like lemurs or squirrel monkeys are especially vulnerable to unwanted animal-human interactions. Whether it is people touching and/or holding the monkeys, people feeding the monkeys things that aren't good for them or monkeys exploring peoples' backpacks, child carriers and so on for food, it always seem to be problematic in some way.
It appears that the only way these kinds of things can be prevented is to have clear rules and to have staff or volunteers present at all times to enforce the rules and to do surveillance. Even that is not a complete guarantee because, well, people can be real idiots.
So I'm not a huge fan of walk-throughs with primates and generally prefer primates to be in exhibits with good viewing, but without possibility of contact.