Anyone who holds a religious faith, or an ideological or philosophical position, is rarely proven wrong. That's what having faith is. For religions make claims that are outside the scope of conventional scientific investigation. Also, behaviors of religious adherents that may demonstrate the undesirability of the religion are always disowned. Thus, Arab terrorists aren't "real" Muslims, "Islam" means "peace," etc. And both history and the present is full of Christians accusing other Christians of doing unchristian things. But somewhere in there is "real" Christianity. Honest. Have faith.
Often it is the case, that anything can prove anything. In developed countries, religious conservatives tend to have far more children, less likely to practice birth control. Liberals do not propagate as many children with liberal values, and thus may become extinct. Does this prove that God blesses the faithful, or does it prove Darwin's "survival of the fittest?" Just asking. And just because we don't have, for example, Communism, doesn't mean we won't; we're just in a stage, a stage that Marx could not have predicted. Liberalism proves that government can make economies grow -just ignore the deficits and inflation. Constitutional democracy is the greatest form of government - which is why the "greatest" one, the USA had to be held together by force and a cost of 600,000 lives. Americans are a peaceful people - which is apparently why the USA has fought countless big and small wars even though it's been nearly 200 years since there's been a serious threat to her security.
If the superstar athlete's team wins several championships, then he's not the greatest of all time because obviously he had a lot of great teammates helping him. But if he never wins the championship, then that also proves he's not the best ever. The homogenization of America - identical strip malls and radio play-lists all over America - proves that America is in cultural decline. But so does the opposite - the creation of diverse niche markets means that America is losing her common cultural heritage. If drug use goes down, that proves that the War on Drugs is successful. If drug use goes up, that proves we're not doing enough.
If you want to believe something, you will always have enough evidence and you'll never be proven wrong. Two major terror attacks in the past two years - in Madrid and London - can be interpreted as proof that we're winning the War on Terror - "only two attacks, none on American soil." Or, it can prove that we are losing the War on Terror and that we can't win it. Terrorism can also prove that the terrorists hate us, our civilization, and our freedom - or it can prove that they just want us to end our occupation of their countries - the terrorists aren't attacking Sweden!
Look at it from the other perspective. Moderates are frequently wrong, and they often freely admit it. "We were lied to about the WMD's." But libertarians, conspiracy theorists, and the far left weren't. "I had high hopes for [Bush or Clinton] and I am really disappointed." But those with low expectations can not be disappointed. The problem with the moderate is that he doesn't have vision, no understanding of the world. Which is better, of course, than having a false view of the world: I read one blogger claim that the "culture war" is just conservative bitterness over Watergate, as if abortion Roe v. Wade nothing to do with it. But the problem, as the old saying - once sung by John Mellencamp on his Scarecrow album - goes, "You got to stand for something, or you're going to fall for anything."
So we have a dilemma. A stubborn belief is dangerous, because even contrary evidence can be interpreted as confirming evidence. But on the other hand, a moderate, undecided, "searching" position makes one easily misled, seduced by trust in authority or a smooth argument.
The resolution lies in values. We must separate that which we genuinely love, our values, from the utilitarian means that supposedly protect and serve them. Do we love the Constitution, or do we love the things that the Constitution was meant to preserve and advance? Is the scientist committed to Darwinism, or to the unbiased discovery of knowledge which he believes Design scientists do not share? Do we love social democracy, or do we want people to live in a tolerant society free from economic monopolies? Do we want a libertarian government, or do we want, well, a tolerant society free from economic monopolies?
Those of us who hate the extension of violence and coercion in society, hate the extension of violence and coercion in society. Thus, if socialism could make us rich and the free market would make us poor, we would still hate socialism. If we can gain a better position through aggressive war, we would still reject those means. Our values rule out initiating force. Others hold on to different values - and find no moral problem with coercing or inflicting violence on other people to advance their them.
Advocates of a free society can not use utilitarian arguments to make their arguments. Some dwell on the good that emerged from a war, and thus believe war is legitimate; I look instead what could have been had the war not been fought (and the tax not imposed, and the censorship not imposed, etc). The reason dialog and persuasion is often impossible is that the gulf between the values the two sides hold is too wide. People can not dialog when they do not understand each other.
In a society and world where people hold fundamentally conflicting values, we should not place our hope in coming to an "understanding." Perhaps negotiated settlements is the best we can hope for.
This is what politics is about.