Does "carnival barker" mean the opposite of "barker"?

I saw the following line in an article in Forbes (April 27) dealing with President Obama’s release of his long-form birth certificate:

"We're not going to be able to solve our problems if we get distracted by sideshows and carnival barkers."

^{-President Obama, on the controversy, stoked by Donald Trump, over whether he was born in the United States}

As I was unfamiliar with the phrase carnival barker. I looked for the meaning on on-line dictionaries, and found the definition: "one who hangs out outside a party and warns people not to go in for any reason" (my emphasis) at Urban Dictionary.

Barker, as I understand, means "a person who stands outside a place where there is entertainment and shouts to people to go in," as Oxford Advanced Learner’s Dictionary defines.

I was puzzled why barker, who is supposed to solicit people to come in, comes to mean one who warns people not to go in simply by being prefixed with carnival. Can somebody explain to me why? Is the definition at Urban Dictionary right?

I think what is going on in the Urban Dictionary definition you found is a description of someone at a carnival who is purposefully using reverse psychology in an attempt to actually get more people inside. I'm getting this from the definition's example sentence (Carnival Barker- "Don't go in there man it's haunted.") For example, such a carnival barker may target a man and a woman on a date. By saying to the man, "don't go in there, it's too scary," he could be seen as indirectly questioning the guy's "manhood," thus convincing him to go in and prove himself.

This is an admittedly confusing definition of carnival barker. For future reference, Urban Dictionary is often useful for very current slang and fun to play around with (try looking up your town or city), but it's not the best place for good definitions. Check out these "definitions" of Urban Dictionary at Urban Dictionary to get my point. And even for definitions of slang, be sure to check the poster's other entries for a sense of their credibility and take note of how many up vs. down votes their entry has.

To summarize:

• Urban dictionary is not very reliable.
• specifically, the example there of implying reverse psychology, is not defining, but rather a very incidental use.
• 'carnival barker' is really not a set phrase so means literally a barker at a carnival.
• 'carnival barker' is almost a tautology. barkers seem to only be at carnivals. OK, maybe a circus.