We don't need to depict here all the crimes Hitler was responsible for - anybody can find tons of documentation about this. The first and foremost perpetrator was Adolf Hitler himself. He was the supreme architect of the operation; without him it would have been inconceivable.
Unlike the perpetrators, the victims were perpetually exposed. They were identifiable and countable at every turn. Jews and non-Jews alike, the victims as a whole, however, have remained an amorphous mass. Millions of them suffered a common fate in front of pre-dug mass graves or in hermetically sealed gas chambers.
What we want point out here, is what Hitler personally though anout homosexuality, and the order he gave to eradicate it.
There are some evidence that Hitler himself had a (consciously or unconsciously - we have no documentation about that) repressed homosexual side and had several gay friends during WW1 and in the 1920'es.
Hitler considered homosexuality as a predisposition that could not be changed. He assumed that a homosexual orientation could not be eliminated, that only its manifestations could be blocked. He openly despised homosexuality and criminalized it.
After Hitler's failed 1923 putsch and his subsequent jail term, he resolved to gain power by working within the German constitution rather than against it. By 1928, the National Socialist Democratic Party was a major political force in Germany. Thus, they were included when questionnaires were sent to all the major political groups in 1928. In their response to the question about homosexuality, the Nazis (if not Hitler himself - but of course with his assent) stated:
"It is not necessary that you and I live, but it is necessary that the German People live. And it can only live if it maintains its masculinity. It can only maintain its masculinity if it exercises discipline... Free love and deviance are undisciplined. Therefore, we reject you... Any who thinks of homosexual love is our enemy."
Unfortunately, along with other prophetic warnings of future persecution and war - most notably those in Hitler's Mein Kampf - very few people paid attention to this blunt denunciation of homosexuals.
One should note though that Hitler himself generally remained distant from this issue. In Mein Kampf, Hitler never mentioned homosexuality. Hitler's only significant pre-Chancellor mention of homosexuality comes in a 1930 conversation with his close confidant, Otto Wagener:
"We must therefore take the view that any sexual involvement between person of the same sex is unnatural, it runs counter to the meaning of pairing and of the divine command: Be fruitful and multiply. That is why any such activity, no matter of what sort, is to be forbidden and punishable as soon as a boy has reached puberty. Besides, pure pederasty seems to me entirely un-Germanic. I feel that it is filth of the lowest order. Pederasts [the word here used as synonym of "homosexual"] should be expelled from the community of the Volk."
Ironically, this conversation with Wagener took place just after Hitler made the decision to appoint Röhm, who was himself a homosexual and a pedophile, to be the head of his own personal militia, the SA or Brown-Shirts.
Hitler, of course, had known of Röhm's homosexuality since 1919, as Röhm himself was careless of his reputation - Röhm was a member of Hirschfeld's League for Human Rights and openly attended homosexual meeting places. But Hitler was not yet strong enough in his own right to maintain power without his help.
Soon after Hitler's appointment as chancellor, the police systematically raided and closed down homosexual meeting bars and clubs, forcing gay men and lesbians to meet in secret. The Nazis created a climate of fear by encouraging police raids and denunciations against homosexuals.
Germany's homosexuals felt the impact of the new regime within weeks of Adolf Hitler's appointment as chancellor. In February 1933 police and Storm Troopers began enforcing February orders to shut same-sex bars and clubs and to stop the sale of all publications with sexual content. During the next several months, most gathering places for homosexual men and women closed, fundamentally disrupting their public lives. The Nazi laws were silent on lesbianism, although individual instances of persecutions of lesbians have been recorded.
Soon after, Hitler himself ordered the arrest of homosexual men within the ranks of the Nazi Party, referring to them as "pigs." Hitler clearly demonstrated his will to systematize the state-sanctioned persecution of homosexuals in a memorandum directed to the SA:
"I expect all SA leaders to help to preserve and strengthen the SA in its capacity as a pure and cleanly institution. In particular, I should like every mother to be able to allow her son to join the SA, the [Nazi] Party, and Hitler Youth without fear that he may become morally corrupted in their ranks. I therefore require all SA commanders to take the utmost pains to ensure that offenses under §175 are met by immediate expulsion of the culprit from the SA and the Party. I want to see men as SA commanders, not ludicrous monkeys."
This could have been a warning for Röhm, but he still felt too powerful to be worried by this message. But as soon as Hitler felt strong enough, and possibly fearing Röhm's growing power, in 1934 he ordered to kill him - his old friend sudden had become an hindrance to him! The official reason for eliminating Röhm was his homosexuality!
Hitler had good reason to be concerned about the reputation of Nazi organizations, most of which were based on strict segregation of the sexes. Hitler Youth, for example, was disparagingly referred to as Homo Youth throughout the Third Reich, a characterization which the Nazi leadership vainly struggled to eliminate.
On the same day that Röhm was murdered, Hitler issued an order to purge all gays from the army, for he feared a Secret Order of The Third Sex. While Röhm and his men were being rounded up for the massacre, the new Chief of Staff received his first order from the Fuhrer:
"I expect all SA leaders to help preserve and strengthen the SA in its capacity as a pure and cleanly institution. In particular, I should like every mother to be able to allow her son to join the SA, Party, and Hitler Youth without fear that he may become morally corrupted in their ranks. I therefore request all SA commanders to take the utmost pains to ensure that offences under Paragraph 175 are met by immediate expulsion of the culprit from the SA and the Party."
The Röhm/SA-affair became a cornerstone in Hitler's and Nazis' anti-homosexuality offensive. An increasing number of gay men was sent to prisons and Concentration Camps.
In 1934, Rudolf Diels, the founder of the Gestapo, lectured his colleagues on how homosexuals had caused the downfall of ancient Greece. He, recorded some of Hitler's personal thoughts on the subject:
"He lectured me on the role of homosexuality in history and politics. It had destroyed ancient Greece, he said. Once rife, it extended its contagious effects like an ineluctable law of nature to the best and most manly of characters, eliminating from the reproductive process precisely those men on whose offspring a nation depended. The immediate result of the vice was, however, that unnatural passion swiftly became dominant in public affairs if it were allowed to spread unchecked."
On November 15th, 1941, in a Decree of the Fuehrer for the Cleansing of the SS and of the police force, Hitler orders the death penalty for homosexual activity by members of the SS and Police. He decleared that homosexuality is a "crime against the German nation," punishable by death.
If up to then the Nazis had aleady persecuted, oppressed and killed homosexuals, now they had also Hitler's explicit approval and blessing!