How can Democrats argue that the "Rich" don't pay their "Fair Share"...?

You are going on the false assumption that they're driven by logic. They can argue the the rich don't pay their fair share because they want to instill an aura of class warfare that they can then exploit and turn into votes and support.

Simply because most "Rich" people who invest their money are not earning wages, and therefor do not pay income tax on their money. They pay capital gains which is taxed at a lower rate than income.

So a person making money from investments might pay say 15% instead of 35% which some not so rich people find themselves in the higher tax bracket because they are earning wages, while the investor is taxed differently.

Math isn't their strong suit. Otherwise, they never would have created Fannie Mae.

Of course you can't simultaneously pay less taxes and receive more refunds, but you have to think about it to understand that. Until then, it sounds good and gets an emotional response out of people..

because according to percentiles of income paid to tax, lower class and upper class pay around 14%, and middle class pays about 36%

this is not an opinion, this is fact, it's almost 2am so Im not going to go surfing for surveys, but I am sure you can find them with relative ease.

edit: I love how "barrack obama" said "because there stupid", hate to tell you this, but you mispelled they're

Don't argue with Democrats.

They are not honest and thus your facts or opinions are of no consequence to their ultimate goal of world communism.

Because there stupid,