"That" or "Who" after a Person

A reader of my new "Watch Your Language" column on writermag.com asked me this:

"What I noticed a lot lately and bugs me is that people will use "that" when they should use "who." For example, "The man that sells ice cream on the corner retired." I always believed "who" should be used when talking about people, but since I see and hear "that" used so much, I started to doubt myself. Am I correct?"

This is a good question. My grammar sources tell me that Shakespeare and the Bible, for example, use "that" after a person. So although it isn't incorrect to use "that" after a person, it's more common to use "who," and I prefer "who."

Stick with "who" after a person, but it's OK to use "that" if you really must.