One of President Clinton's staff was famously (either mythically or really) quoted, saying: "Yeah, power corrupts, and absolute power is pretty cool...".
The problem facing dissenters is not whether they are "right", or "good" or even focused on a real problem. In a "free" country (so far) the only questions with dissent are legal ones: Are the dissenters harming other citizens in their act of dissent and does government deside that dissent is so politically dangerous to the status quo of society that it must be stomped down?
Who decides legitimacy? Unfortunately, it is the people in control of the government, and very often they are at odds with the concerns/best interests of those citizens in dissent. The penalty for not being "legitimate" can vary. Since we are talking The United States and not Russia, dissenters are more likely to be "investigated" than jailed or killed (so far). But there will probably come a time when that will change.
So legality can't really be allowed to be the issue. Truth is the issue.
Who decides when those in power have gone too far, and when to take true dissent past the point of legality? In this country and at this moment the Democratic Congress is saddling the people with as many big-government programs as can possibly be crammed into what's left of Obama's "political capital".
I'm not certain how much power the 0-man actually has over this Congress. But the cool thing for him, is that he can always blame socialist extremes on the far-left wing of the Democratic Party. It really takes the short-term heat of of him.
This is another argument for a line-item veto, even if it does increase executive powers. It sure would put a lot more pressure on the President to be right about everyhing, or lose the public relations battle.
For those of us who have long been in true opposition to big government and all of the supposedly "legitimate" doings that come with the abomination, we consider the Obama administration as simply the continued growth of the Bush administration, keeping a growing federal government growing ever larger and more incompassing, decreasing state's rights, and as a result, stifling individual freedom and liberty.
These anti-bailout, anti-tax tea parties are a good thing. They keep the problem fresh in the public's mind, as well as draw Uncle's attention and give cover for those who are really serious about change.
We need a national sales/flat-tax combination, and we need to do away with the IRS. If our government keeps screwing us, there will be some sort of revolt, whether for good or bad.
My point is not to continue to rail against Obama, but to make the point that dissent is still "legal", and the definition of legitimacy has two meanings (legality and truth), in this example neither of them pitted against one another, UNTIL government moves on dissenters.
As of right now we are all permitted to put whatever "premium" on whatever opinion we want to -- or this is not a free country. And "credibility" seems to be very subjective. Just look at the views regarding Keynesian economics (voodoo, if there ever was). The real problem is when government starts stifling expression to "preserve society".
True, these particular Republican Tea Partiers are fakers. But there are real Tea Partiers who may yet play their hand, if things go the way I think they will. With the burdans of social programs growing on the taxpayer, there will come a time when there will be a real Tea Party, and then the 0-man will really have the opportunity to act in a disturbingly Lincolnesque way....
Hope and change, baby. Hope and change.