I am sorry but AlterNet and amerikanbeat are not even remotely credible sources and if your satisfied that they have provided you the information you need to have an opinion on this topic then I can not debate you (yes I did read both links and it is complete garbage in my opinion).
ElasticNinja brings up decents points but his ideas are based on the assumption that most wealthy people are business owners. I am pretty sure that is not even close to reality (I could be wrong but have not looked up the stats). A wealthy person can be wealthy without owning a business and therefore most of his arguments are moot.
None of these arguments wants to address the fact that wealthy people essentially fund the government with their so called "unfair" share of taxes. That allows the government to do all these things that you argue they are getting. You then run into a chicken/egg problem.
In my opinion they get very little if anything in return and could function fairly well without all those so called government perks they receive. The poor that receive all the government assistance and pay nothing into the pot, assistance that can be measured in actual dollars instead of theory, would have a must harder time functioning.
Ok well I don't know what those web sites are but I don't think what they say is garbage. Also, several of the points listed there are really the same points that ElasticNinja mentioned -- so it seems a bit odd/contradictory to me say that those links are total garbage but then say that Ninja's points are valid. I'm a little confused by that but that's really not the issue here.
I have to agree with you in some sense -- you're absolutely right that many of those benefits really only make sense to people that are running business (be they owners, CEOs, board members, etc.). I also agree with you that those who are already wealthy would probably function just fine without those perks, and that the poor would struggle. So isn't that justification for a progressive tax rate? I know most opponents to this are going to say "well that's just mixing morality into this -- there is no logical argument that they should be required to pay more." However, I think that there is (beyond the fact that it *is* required because it was written into law by our predecessors).
If you tax all people at the same rate, you are disproportionately affecting the middle and low income. I already believe that it's impossible to raise a family (and possibly even be single) on minimum wage. If you start taking even more of that already scarce resource then you won't have any economy. Who do you expect to buy all of these new electronic gizmos and so forth? Who do you expect to buy tickets to games for all of these sporting events where athletes are paid millions of dollars/year? This money comes from people consuming these goods and services. If there is only a small amount of people who can actually afford to do that, then there is no economy. At some point, the wealthy have purchased what they need -- there is just no incentive for every wealthy person in the U.S. to purchase 20,000 iPads (as opposed to having a large number of middle-class people purchase them). In such scenarios where too many people have nothing you usually just wind up with a revolution.
This is one reason why I think the fair tax makes a lot more sense. People aren't taxed on their income but rather their expenditures. If you spend more money then you pay more taxes. Very simple. Of course it would also put thousands of people that work for the federal government out of a job so they would not have income to spend until they found a new job. But then again taxes would be much easier to calculate so the government wouldn't need to spend all of that money to have people review tax returns in such a complicated system.
I do however think that 23% is too high for low income people to pay. Again, if you're only making $15,000/year on minimum wage then chances are you are spending all of that amount every year on rent, groceries, etc. Thus, they are really getting about $11,500/year which is just insanely low to expect anyone to raise a family, etc. Even a single person will have a hard time living off of that. Rent at reasonable places in my town is usually at least $600/month for a single bedroom apartment. That's already $7200/year. Then car payments, gas, insurance, medical bills, food, etc. Good luck...
Maybe it's just that I don't make millions of dollars/year and if I did I would see things differently. But making so much money that I get to whine about being taxed more sounds like a good problem to have if you ask me. If wealthy people don't like their tax rate then they can always stop making that much money by changing to a lower paying job. If there are any millionaires out there who wish to trade salaries with me I will accept your call any time! (Ok I'm playing a bit of devil's advocate here but still...call me).
Whatever happens I still have a few ideas to raise revenue:
1. Legalize pot and tax it
2. Legalize gay marriage and get a boost from all of the incoming marriage licenses (though this income would probably be very significant at first and then taper off until it was only a tad more than what we currently have now). Bonus: You'll get to have courts/states making money off of all the gay divorces that occur too! (Yes -- that's a joke though there is a nugget of truth to it).
Forgetting the unemployed (the majority whom, certainly at this point in time, do not wish to do so), I think its hard to argue that the poor benefit multiples more from the government more than the wealthy. If anything the the lower income strands of society are government subsidised labour for the wealthy. 
