Some people use “I don’t want to argue.” as a club in discussion.
Certainly, arguments can get unpleasant if people do it wrong. There are various lists of argument fallacies, such as http://en.wikipedia.org/wiki/List_of_fallacies.
That is not a good reason to forbid arguments. One definition of argue is “to give reasons (for or against)” (Webster’s New World Compact Desk Dictionary and Style Guide / Second Edition, © 2002 by Wiley Publishing, Inc. Cleveland, OH, ISBN: 0-7645-7120-6)
Doesn’t this sound like a discussion? Wouldn’t you want an issue to be discussed thoroughly?
And lastly, have you noticed how often people who use “I don’t want to argue” have already argued their case and use this line to deny others their say? Not very nice, is it?