I'd like to invite people who think progressive taxation makes sense to define the word "fair".
I don't particularly like the word fair, it seems to be used very subjectively. I would personally define fair simply as equitable treatment.
Life certainly isn't fair. It isn't fair that I was born in politically stable Australia while so many were born in the tumultuous regions of the middle east, africa, venezuela etc...
It isn't fair that some people get born with horrible diseases, disfigurements or ailments.
It isn't fair that some people are born geniuses while others cannot even tie their own shoelaces.
Those of us privileged to be born into relative wealth (whether that be financial wealth, intellectual wealth or just a wealth of virtue) have a weak responsibility to share our unfairly bestowed wealth with those less fortunate.
But it is not a requirement that the wealthy share. When those who are the recipients of generosity from the wealthy begin to feel entitled to the incredible kindness bestowed upon them, the wealthy must be allowed to withdraw their support. Without consent from the owners of said wealth, the transfer becomes immoral - it becomes theft - and society becomes a race to the bottom. Any removal of someone else's property without their consent is always and forever theft. This is by definition and has nothing to do with law.
These dysgenic forces will destroy modern day society just as they have in the past.
The wealthy (again whether financially, intellectually or personally) are a gift to us less fortunate simply by being who they are and doing the cool things they do. Those of us who are less fortunate need to recognize this. This is the christian virtue of humility.
The only way to maintain a stable society (not to mention morally consistent) is through voluntarism and the only way to increase voluntarism is by shrinking the size and power of the state.