The two young ladies were very pleased. I made sure the dog could not see his owners (both sitting to my right), and would allow him to see them only once he was calm. He did not dare show me his teeth, growl, or bite afterward.
After his owners told me that this tough, little guy showed aggression towards larger dogs, I had another dog owner walk by a few times with both of her tail-wagging black Labs, as I held the little guy on the ground. The Labs very kindly introduced themselves to the Chihuahua, with barely a peep from the latter. We did this about a half dozen times.
This was the first time his owners could remember that he did not lunge or bark at the larger dogs. I insisted, rather drilled it into them, that these corrections must continue with them, lest his aggressive behaviour persist. I hope the bite on my knuckle and ensuing sepsis were not in vain.

An absolutely adorable Chihuahua.