Awwww... Predator behavior.
It's not that the kid's in zebra stripes that's getting this lion worked up. It's that the kid is a baby, and looks like what prey should look like to an alpha predator.
Some might be upset that mom and dad left their kid to clearly be a lure for such a shot. I submit, though, that if we stipulate that thick safety glass is beyond an African lion's ability to defeat (and so far that's been the case), the kid is far safer here than being dressed up for a child beauty pageant, or sent to cheer-leading camp, or stood near a mountain stream for a nature shot. It's all the same. "Look at my kid!"