In this case, the [[propaganda]] technique may merely be an attempt to tack "bad science" as a negative [[buzzword]] onto whatever is being attacked. It may be effective because counter-arguments against these claims are long, complex and difficult to understand.
These accusations are typically levied by [[think tank]]s and [[public relations]] firms under order from [[tobbaccotobacco]] companies and businesses that have something to gain by denial of [[global warming]].
Unfortunately, some claims of bad or junk science really are legimate, and sometimes these are mixed with accusations that are completely bogus.
* http://www.junkscience.com/ - Combines "junk science" accusations with vitriolic anti-liberal diatribes. Author affiliated with the [[Cato Institute]]