Dressing the baby in zebra-like stripes seems intentional which makes them plain mean as well as ignorant and negligent.
But, even if their intent wasn't to tease the lions purposefully and the colors were picked by accident, they still should have immediately picked up the child and removed him from the lion trying to get at him through the glass.
I am assuming workers did not see what was going on because if they had they should/would have had security remove them immediately for agitating the animals. How negligent to the child and how cruel to the lion to let that continue for as long as it did. Hopefully they are banned from the zoo.