I see no problem with it myself. It's just a tool to assist in getting a good end result.
Think of the situation before tuning software came along. Singers didn't walk into the studio, do one take and that was it. It has always been (and still is) standard practice to do multiple takes and use...
You can't if it's used subtly on a vocal take of a reasonable standard. Most studios will use it in this way to add polish to a vocal as I stated earlier.
I'm guessing (and forgive my presumption if I'm wrong) what CBH is referring to is the use of it as an 'effect' (Cher/T-Pain style) which is...
It's digital software that cleverly corrects the frequency (pitch) of a note without altering its speed/length.
The actual 'Auto-tune' software is developed by a company called Antares, although there are many other pitch altering software programs available. The best, and arguably most popular...