Most libertarians and conservatives, with the exception some paleocons and left-libertarians, are staunch opponents of trade unions. Warner Todd Huston, a rather eccentric "conservative" (and from his picture, evidently a donut-eating contest winner) has said "unions are inherently unAmerican", a belief not uncommon on the mainstream right. Libertarian/anarcho-capitalist Lew Rockwell even titled a UAW-related blogpost "Another Criminal Strike". Indeed, the LewRockwell.com writers in general frequently refer to unions as criminal gangs.
As a libertarian, I oppose the privileges granted to unions by the federal government, but nor do I like the privileges granted to corporations and groups of corporations by all levels of government, including eminent domain takings, tax increment financing, subsidies, and insane copyright laws such as the DMCA (which in no way "promote(s) the Progress of Science and useful Arts", but that's a topic for another day). Corporations themselves are government creations and receive special protections and privileges from governments. Now, I realize that libertarians criticize corporate welfare and Big Business, but it is ludicrous that conservatives and Chamber of Commerce libertarians will call Big Labor criminals and anti-American while at the same time verbally fellating Big Business, which can be pretty criminal and anti-American itself (i.e. hiring illegal immigrants).
Sure, the SEIU is probably close to being a criminal organization, but I doubt anyone could honestly call the bricklayers union a group of thugs. In some trades, joining the union means higher wages and better benefit, so it makes sense for the workers to join unions, just as it makes sense for different corporations of certain fields to form trade associations to protect their interests and for white-collar workers to join professional organizations (for example, the IEEE).
The union most frequently targeted by conservatives is the National Education Assocation (NEA). The conservative hatred of the NEA is comparable to the liberal hatred of Wal-Mart. Yes, the NEA is dominated by liberals and feminists, but whenever a conservative bashes the NEA, inevitably they bring up its policies that affect "urban students." These commentators correctly note the fact that urban schools, well, suck.
However, the fact that urban schools suck has nothing to do with the NEA. Suburban students are taught by NEA members and they have decent test scores. The fact is, urban schools suck because they are predominantly black and Hispanic, while suburban schools are attended by whites and Asians. Blacks have a mean IQ of 85, Hispanics 89, Whites 103, and Asians 106. Lower IQ students will simply do worse in school than higher IQ students. Neither the liberal solution, spending more gigadollars on urban schools, nor the conservative solution, abolishing the NEA (and giving the black kids vouchers), will solve this.
Yes, this post was supposed to be about anti-unionism, but I wanted to point out how far conservatives will go just to prove that they are not racist to liberals who will hate them anyways and blacks who will never vote for them.