I only do it with those I know well. Especially since when you know them very well, you can pull personal experiences and their personal situations into the arguments.
I did this to my aunt who is a big time looney lefty. She was complaining about the republicans wanting to get rid of the inheritance tax and that it was unfair and that the rich should pay. She doesnt not consider herself or her family "rich" but she does consider them to be "lucky" and "fortunate" as all liberals do.
Well, upon her demanding the GOP not repeal the death tax I asked her a simple question... "Aunt Chris, if you and uncle Bob died tomorrow in a car accident where would Teresa and Jessica (their daughters) get the $400,000 to pay the inheritance tax upon receiving your estate?"
She wondered why they would need to pay it, after all they are not "rich". And then I broke down her net worth for her (which i knew from financial dealings with them) and what the kids death tax bill would be. It made her look at it a lot different since it affected her and not just Bill Gates and his buddies.
An old girlfriend of mine is a democrat and liberal. Just prior to the election i sent her an email "Just for fun, why are you a democrat?" Her response was "Because I care about people and you seem to only care about money." I have yet to pen a response as I want to do it properly and not 'off the handle'.
But it will start out something like... "Your response to my questions is like all of the democrats agenda, ideas, and answers... empty, lacking thought, and symbolism over substance.'
This is sad. Your friend says she's a democrat because of YOU? And what a creep you are?
Trust me, this person is too stupid to know you. Wipe her out of your address book immediately!
That might help you feel better but it will only start a fight and galvanize her position, reinforce her prejudice, and "prove her point" in her own mind that all conservatives are nasty, selfish, oppressive, etc.
A better approach, if you're actually trying to convert her, is much like religious conversion (IMHO it _is_ a religious conversion) - neutralize her opposition with kindness and understanding, and lovingly try to point out the shortcomings of "her" way and try to convince her of the benefits of "your" way and her need to adhere to it.
I know this sounds wimpy, but I really think it's the only way. I would hazard a guess that no liberal has ever been converted to conservatism by unassailable logic conveyed in the context of a heated argument.
I don't think that tack will win friends or positively influence people.
My approach would be to explain why favoring a person's keeping his own money is the best way to care about him.