This is, of course, a specious argument. Anarchism was very active in the United States at the beginning of the 20th century, and the work of these early anarchists led to things like the eight-hour work day, improved working conditions, and the elimination of child labor, initiatives that made them very unpopular with capitalists.
Beginning around 1901 and 1909, (particularly after 1901, when US President McKinley was assassinated by a self-proclaimed anarchist) a series of measures were instituted in the US, designed to stamp out this vibrant leftist revolutionary movement. This policy was further expanded under the Wilson Administration, in his effort to quell domestic dissent during World War I (via the Espionage Act of 1917 [and the amended Sedition Act of 1918]). Anarchists bore the brunt of these initiatives, which was the full intention of legislators of the time.
[A comrade from New York recently looked into the NY penal code, coming up with the below ordnance that is still in effect; this code likely is in place throughout the country; research your own state's penal codes to see where anarchists stand in the eyes of the law!]
Established political offenders (represented by parties, like the Communists, Socialists, even Fascists) were treated with relative leniency. Anarchists, in their eschewing of party politics and organizations, were exempted from this clemency. As a result, it became "safer" to be a card-carrying Communist or goose-stepping Fascist than an anarchist--because even if you were involved in the same revolutionary activities, if you were an anarchist, you were considered merely a criminal, and not a political offender. Consequently, this policy snuffed out the indigenous anarchist movement in the United States, as prominent anarchists were either jailed, deported or executed.
Why this "special" treatment? Simple. Anarchists alone are the truest threat to government because they do not "play ball" via party organizations, platforms, leaders and spokesmen, parliamentary reformism, and other institutional mechanisms of authority, manipulation, and coercion.
In this sense, Fascists, State Communists, Democrats, Republicans, Libertarians, Democratic Socialists, and other "legitimate" political movements all resemble each other more closely than they resemble anarchists, regardless of their place on the political continuum. All of these ideologies function amicably within the capitalist economic system (whether state-run capitalism like the US, China, or the former USSR, or more laissez-faire capitalism like the various "banana republics" of South and Central America), and are treated in kind.
This is how the United States is able to deal on such cozy terms with fascists all over the world, and could look the other way when China butchered its own pro-democracy movement. All of these agencies are comfortable with the idea of a powerful elite, privilege for some, masters and servants. Only anarchists oppose this without exception.
Accordingly, only anarchists have been singled out as "enemies of humanity," because of their opposition to the state. Even hate groups are granted legitimacy in the eyes of the law--in the United States, it's more politically acceptable to be a neo-nazi than to be an anarchist! Given the good that anarchists have brought about, versus the evil perpretrated by fascists, this is a grievous insult.
Anarchists are the direst threat to the state, which is why they have been so harshly oppressed. If enough people hold anarchist ideals, the very legitimacy of government (and of course, capitalism) is seriously challenged.
The merits of anarchism are meaningless, however, when crossed with the will to preserve the state--the servants of the state will do whatever they have to in order to remain in power; such are the "principles" established by Macchiavelli himself in The Prince. In other words, it doesn't matter that anarchists are right in their quest for diversity, unity, brotherhood, liberty, and equality; because they challenge the legitimacy of the state, they become the "bad guys." Such is the fate of anyone who challenges the state, something that "reformists" and parliamentarians have yet to learn, unfortunately.
Anarchists ARE enemies of a small sector of humanity: that is, the despots and profiteers who gain by ensuring the misery of others. If governments wish to define this micro-fraction of the world's population as "humanity," then we are, of course, guilty. If your own definition of humanity is a tad broader than the top 5% of a country's wealthy, then perhaps you have more in common with anarchists than you thought!
In anarchy, only would-be tyrants are oppressed. It is a system without Caesars, Napoleons, Hitlers, Stalins, and a thousand other despots who have left their mark on the world in the blood of innocents. Anarchism means a world of brotherhood, mutual prosperity, and freedom. If believing in these things earns one the brand of "enemy of humanity," in the eyes of the State, then does that mean the State stands for hatred, poverty, and slavery? Why else would it oppose the efforts of anarchists so forcefully? Must all suffer so that some can gain more than they would ever need? The States (and political parties) of the world give an emphatic "yes;" anarchists alone give an outraged "no." Where do you stand?