Let's explore:
Clearly various liberal sources, including Bill Clinton himself, believe that the wealthy not paying more in taxes is an issue of morality.
I think there's a clear distinction between - on the one hand - the morality of Republicans in creating and maintaining a system that allows the wealthy to pay even lower tax rates than the middle class, and - on the other hand - the morality of the wealthy who merely minimize their taxes under the system Republicans fight so hard to maintain.
In fact, this gets to the heart of the situation with the Clintons: They are advocating for a fairer tax system, even though under that system they would be forced to pay more. It's their advocacy that's moral; their payment of taxes under whatever system exists is amoral. On the other hand, a wealthy person who fights to maintain or even increase his tax advantage is being unreasonably greedy - immoral; but, again, his adherence to whatever tax system is in place is amoral.
You honestly think that when liberals throw around terms like the 1%, the Buffet-Rule and paying one's "fair share" they aren't characterizing the income gap and the [lack of] taxes paid by the wealthy as a moral issue?
See my paragraph above: It's the system that allows the 1% to continue to pay such low taxes that's immoral. The "fair share" is the share that the liberals want the tax system to dictate. Are you claiming that liberals are telling rich people to voluntarily pay more than what is owed under the current tax rules? No, they're fighting to change the unfair, immoral tax system.
Okay, here are two non-moral examples. Advocating for a law requiring people to store their garbage cans in a location not visible from the street excluding the 24 hours immediately before and after a scheduled pickup is a criticism of those who keep their trash cans in the front yard. If you keep your garbage cans there despite the failure of that law, you are a hypocrite.
Advocating for a law limiting downtown parking to 2-hours is a criticism of those who park there for longer. If the law doesn't pass and you park your car there all day, you are a hypocrite.
But I think these ARE moral issues. Those who store their garbage in locations visible from the street are making the community look ugly, affecting everyone nearby. This is similar to playing loud music in public, which any sensitive person knows upsets those nearby. Anyone advocating laws on these behaviors is in fact making a point about being a good citizen, a considerate neighbor. So, yes, if they then store their garbage cans publicly or play loud music, they are both bad neighbors AND hypocrites. The same goes for your 2-hour parking example. And for driving exactly 55 miles an hour in the left-hand land, with 20 cars piled up behind you.
Compare this with a person taking full advantage of the tax code: Who around that person is directly affected by their behavior? Who sees an ugly community? Who is irritated? Who cannot find parking? Who is held up in traffic for no good reason? All you can argue is that the year's deficit was $20,000 greater (out of $500,000,000,000) because the person took full advantage of his tax benefits.
I'm focusing on how liberals behave in comparison to their own moral beliefs regarding the payment of taxes by the wealthy. The way liberals talk about taxes on the wealthy, they certainly seem to think it is about morality.
Liberal argue that the system is immoral, not the rich individual's behavior.
The whole argument that one voluntary extra payment would be stupid is a non sequitur that is used to rationalize behavior so the person doesn't feel bad. The government can spend any increase in tax revenues, even if some people don't pay the increase. Thus, an individual's contribution is independent of others' contributions, and said individual can be assured with 100% certainty, that their contribution, no matter how small, will be used. Every little bit counts, so go ahead and pay that little bit extra.
To help you recognize that the argument is a rationalization, here's the same argument on a different topic: "My individual carbon footprint is a tiny fraction of the world's, so there is no point in trying to reduce it."
There is also the issue that a political leader such as the Clinton's putting their money where their mouth is may encourage other wealthy liberal politicians to follow suit.
This is a totally bogus argument. You're essentially arguing that liberals should allow the right-wing rich to 'free ride' on the good will of the left. I can already hear the arguments of the right: "Well, the left has paid down the yearly deficit to half of what it was before; I guess we don't need to raise taxes anymore"
Furthermore, as I wrote before, most people who feel guilty about how little they pay in taxes give more to charity. Why would anyone pay an extra $100,000 to the federal government, where most of the money will pay for programs they don't particularly care about rather than pay that amount to a favored charity?
Furthermore, I feel that the right is playing games when they make your argument, because it changes the focus from the advocated change in the tax law,
which would raise tens or hundreds of billions of dollars every year, and instead debates the morality of the advocate. In effect, rather than engaging in a debate about the morality of the existing tax law, the right is engaging in an ad hominem attack against those who advocate a change in the law.
To put this another way: Let's suppose your argument is true, and advocates for higher taxes for the rich are hypocrites because they don't voluntarily pay the higher taxes they advocates.
What does THAT have to do with whether the advocated law is good or not? Why are you side-tracking the debate?
Are the Clinton's planning on reducing their charitable contributions if tax raises on the wealthy are enacted? If no, then their charitable contributions don't justify their failure to pay the taxes they believe they should owe. If yes, then I would question why it would be beneficial to increase taxes when that will hurt charitable contributions.
Also, I presume that since that organizations such as the American Red Cross get large amounts of donations, I shouldn't bother increasing my donation by a few bucks because it won't make a difference.
Guilty liberals will probably get stuck paying both higher taxes (once new laws go into effect) AND the higher amount of charity, since they would feel guilty cutting back on charities (even if they really want to). In other words, once a certain level of charitable given is established, it's difficult to give less in the future. I say this from personal experience.
Your second point is bogus: The amount by which ADVOCATES of higher taxes reduce their charitable giving in response to new tax laws is irrelevant.
Remember, the purpose of the advocated tax law is to increase taxes on ALL wealthy people, not just liberals with guilty consciences who are advocating for the new law.