PODDing PPs that said his request wasn't unreasonable if you were louder than you realized, but his parting "shot" was rude/PA.
I tend not to talk on my cell when I am in places like that because I get distracted and even if I weren't "cell yelling" I would not care for eavesdroppers, inadvertent or otherwise. I can also say from personal experience that it is often really
hard to tell if you are being too loud on your phone.
FWIW, I read an article once that explained that any overheard phone conversation (cell phone or not) is annoying to a third party who hears it because you only hear one side of the conversation. Apparently it is inherently distracting to your brain because your mind automatically starts trying to figure out the missing pieces of what you are hearing. This means that even talking at a "normal" conversation volume can be more distracting when done on the phone.