The crowd had definitely never seen a king or any other member of the royalty in their life.
And certainly not one all dressed up in chains.
Thus upon seeing them now, they cheered.
And then swept up by the ongoing spectacle, they took the opportunity to mock and jeer at them to their heart's content, not wishing to miss out on this once in a lifetime chance.
"That's the king? The one that kneeled in front of our lord?"
"He looks so young! No wonder he lost!"
"Hahaha! Hey pup! You grown anything down there? Or is it all smooth?"
"Heh heh! Forget about that! He must still suckle on his mommy's tits!"
As Perikles proceeded through the streets, he could hear such and many more crass words being directed towards him, the taunts stinging him immensely, and causing him to swear in his mind.