While seen by many as the first steps in breaking down some of the social, economic and other barriers thrown up by the state to make life harder for GLBT people, there are those who choose to understand the riots purely as social unrest and unnecessary violence.
I choose to neither condemn or approve of precisely what unfolded on June 28, 1969. It is a matter of historical fact that the riots happened, and that they were violent.
However, it is not so difficult to understand the reaction to the Stonewall Inn raid when one begins to examine the social, legal and political environment which the GLBT community in the United States found itself facing.
Consider the following: (via Wikipedia)
Spurred by the national emphasis on anti-communism, Senator Joseph McCarthy conducted hearings discovering communists in the U.S. government, the U.S. Army, and other government-funded agencies and institutions, leading to a national paranoia. Anarchists, communists, and other people deemed un-American and subversive were considered security risks. Homosexuals were included in this list by the U.S. State Department in 1950, on the theory that they were prone to blackmail. Under Secretary of State James E. Webb noted in a report, "It is generally believed that those who engage in overt acts of perversion lack the emotional stability of normal persons." Between 1947 and 1950, 1,700 federal job applications were denied, 4,380 people were discharged from the military, and 420 were fired from their government jobs for being suspected homosexuals.
Let's be clear here, McCarthy's paranoia and hostility basically included anyone who didn't think and act in some stereotyped way that McCarthy and his allies had dreamed up. This is but one of many factors that played into creating a social pressure cooker that was going to go awry sooner or later.
Cities performed "sweeps" to rid neighborhoods, parks, bars, and beaches of gays. They outlawed the wearing of opposite gender clothes, and universities expelled instructors suspected of being homosexual. Thousands of gay men and lesbians were publicly humiliated, physically harassed, fired, jailed, or institutionalized in mental hospitals. Many lived double lives, keeping their private lives secret from their professional ones.
Now we get more into the heart of the issues that ultimately led to and provoked the Stonewall Riots. We aren't talking about the US Federal Government running its own little "Spanish Inquisition" to ferret out "enemies of the state", but also of an atmosphere of systemic criminalization and discrimination against GLBT people in their day to day lives. As revolutions around the world, and throughout history, have repeatedly shown, it is unlikely that such a harsh form of oppression will be sustainable. Even the Magna Carta's roots are in an uprising against abuses of power.
Closer to the Stonewall Inn itself, we have the following environment being fostered by the politicians:
By the early 1960s, a campaign to rid New York City of gay bars was in full effect by order of Mayor Robert F. Wagner, Jr., who was concerned about the image of the city in preparation for the 1964 World's Fair. The city revoked the liquor licenses of the bars, and undercover police officers worked to entrap as many homosexual men as possible. Entrapment usually consisted of an undercover officer who found a man in a bar or public park, engaged him in conversation; if the conversation headed toward the possibility that they might leave together—or the officer bought the man a drink—he was arrested for solicitation. One story in the New York Post described an arrest in a gym locker room, where the officer grabbed his crotch, moaning, and a man who asked him if he was all right was arrested. Few lawyers would defend cases as undesirable as these, and some of those lawyers kicked back their fees to the arresting officer.
So, in New York, we have a situation where the police were engaging in entrapment - clearly this is well before any laws that made entrapment illegal. I don't think it's terribly difficult to infer from this that the GLBT community in New York would be less than trusting of the police.
But wait, it gets better.
Police raids on gay bars were frequent—occurring on average once a month for each bar. Many bars kept extra liquor in a secret panel behind the bar, or in a car down the block, to facilitate resuming business as quickly as possible if alcohol was seized. Bar management usually knew about raids beforehand due to police tip-offs, and raids occurred early enough in the evening that business could commence after the police had finished. During a typical raid, the lights were turned on, and customers were lined up and their identification cards checked. Those without identification or dressed in full drag were arrested; others were allowed to leave. Some of the men, including those in drag, used their draft cards as identification. Women were required to wear three pieces of feminine clothing, and would be arrested if found not wearing them. Employees and management of the bars were also typically arrested. The period immediately before June 28, 1969 was marked by frequent raids of local bars—including a raid at the Stonewall Inn on the Tuesday before the riots—and the closing of the Checkerboard, the Tele-Star, and two other clubs in Greenwich Village
So, not only do we have an atmosphere of legal oppression levied against a group of citizens, but there had been an increase in police raids.
Further, laws which attempt to dictate that men must dress like men, and women like women falsely presuppose that the state has an interest in defining what is "masculine" clothing and what is "feminine" clothing. It does not, and worse, it is next to impossible to define that in any reasonable sense. Such laws are nothing more than blatant attempts to criminalize the fundamentally harmless activity of cross-dressing. In many respects, these raids impacted the transgender part of the population disproportionately although I imagine a fair number of "butch" lesbians were caught in the same net.
Whether the Stonewall riots were "unnecessarily violent" or not is immaterial. One cannot reasonably examine the riots themselves in a vacuum without giving consideration to the environment which gave rise to them. Any population that is actively suppressed from living peaceable lives will sooner or later rise up against their oppressors. While the New York police might have only been the instruments of oppression, it was with them that the GLBT population in New York ran into constant conflict. What happened in 1969 has happened before in other contexts - it only took a few cross-dressers deciding it was time to fight back for the rest of the people in an already tense situation to follow suit.
The issue is not, as some would claim, one of mere momentary violations of rights, but rather the consequences of a protracted campaign of oppression, harrassment and abuse at the hands of the state.