Changing Minds??

I've seen this quotation (without a source) in a number of places:  "I don't share my thoughts because I think it will change the minds of people who think differently; I share my thought to show the people who already think like me that they're not alone."  A few days ago, I posted a little piece call "Got Hope?" addressing this issue of why we write and who we write for.  Maybe it's all of these reasons: to change minds, to share with those who agree, to figure out complicated issues, and to manifest hope.  Does writing for more than one reason improve our writing?  I think so.