Especially when the ideals are based on hate and cruelty.

I believe that was the magazine "Ostara" or something like that? As I understand it, the significance of groups like the Thule society was not their occult activities, since this was the heyday of the occult, where societies and groups were a dime a dozen. But, that being said, when Anton Drexler founded the German Worker's party, the issue of race "jumped" from the Metaphysical sphere to the political. Before this, the race-based Volkisch ideologies of various groups was mystical and had little to do with the "real" world. People cast runes on mountaintops, channeled the Ancient Aryans, and lamented that the "golden age" of their Aryan dominance was lost in the mists of time, and the Germans had been cheated of their "true" heritage. But with Drexler's party and various splinter groups, it was as if they were sitting around moaning about the decline of the Aryan race, and then someone jumped up and said "Well, by god, just what are we going to do about it???"
Even the Shoah was not a clear, defined goal, but the product of about eight years of meandering around. The Third Reich was incredibly inefficient. Hitler's first solution was simply to get Jews out of Germany, and emigration was the most effective means. Eichmann even worked with the Zionists and got about 60,000 to move to Palestine. But with the war, suddenly vast amounts of territory with large Jewish populations fell under German control,a and that's when they started looking for means to eradicate them. Russian Slavs were also to be eliminated: one third would be killed, one third would starve, and one third would remain as slaves until they were worked to death.
The Euthanasia program laid the groundwork for the methodology of extermination, and this was the first mass use of gas chambers after various other means were tried. But more importantly, it also showed that the German medical profession was willing to go along with it with no scruples. The decision to exterminate the Jewish population was probably made in the fall of 1941. One of Eichmann's memos was found in recent years that alluded to a directive from Hitler about this time.
There was resistance to the idea of Extermination, but this was on the grounds that manpower resources would be lost to the German war effort, not out of any moral considerations.
Well, I'll stop now before it gets too boring, not to mention OT.

Yes I remember it was Ostara. The question is about resonsibility, and these people shared the same hate with Hitler. I need no direct causal connection to see some reponsibility. The question is whether the gothic scene is responsible for the Littleton Colorado Massacre and I can't see any connection in this case, because I don't know any contents which are calling somebody up to kill other people. I know there are some black or deathmetal bands who do so, but they are not a part of the gothic scene and I got no problem with censorship if somebody wants to burn down churches or something like that. Gothic is less connected with hate, but with sadness. I mean are the Beatles responsible for Manson's massacres? Gothic creates a free space through breaking societal norms, morals and taboos, but there still are norms. Gothic is non violent for example. Murder is the worst possible form of violence and the meanest way to destroy freedom. Gothic is a little bit sophisticated, might be some people are to stupid for.

If we are talking about shared responsibility for the Shoah, then the net gets cast much, much further than the occultist groups. Anti-Semitism was common in Eastern Europe, and in many cases the local population was only too willing to help round up Jews. Jewish partisans likely to be disarmed and shot by Russian partisans, ostensibly fighting the same enemy. Contrast this with countries such as Denmark and even Italy, where the population made a concerted effort to thwart the roundups. The number of foreign divisions in the Waffen SS is another indication. Dirlewanger was so brutal he even disgusted the SS.
But as far as Littleton, I have always thought it is typical how the "gothic connection" was debunked very shortly after the massacre, but this never made it into the national consciousness.The original inaccurate reports are still bandied about, particularly on religious-affiliated sites.
With the whole question of whether music, games, books, etc can be held responsible for someone's actions, I have always held that this is ludicrous, no matter how much I may dislike the particular medium. If someone can be inspired to commit a crime by a song or a movie, this is an indication of much deeper and serious problems that would be manifested sooner or later anyway, under one pretext or another.

I wouldn't say the black/death metal scenes are truly disconnected from the gothic scene. They are simply taking the goth aesthetic and superimposing it onto extreme metal. I would say, at least nowadays, they are part of the extended "schwarze szene" or "dark music" family.
The bridge has always been there since the early days of Venom, Celtic Frost, Mercyful Fate, and Black Sabbath, not to mention crust punk bands like Amebix borrowing aesthetics from both scenes, or goth bands like Fields of the Nephilim borrowing from metal.

The main point of contention between the two scenes, however, is the one of advocating violence.
However, I believe back in time the goth scene was not so pacifistic as it is today, at least according to members of Sex Gang Children, especially when it wasn't really differentiated from the punk scene.

I would not say pacifism or aversion to hatred is truly what defines the gothic scene, however. I've always seen it as more "brains over brawn" in that respect. Looking at things from an idealistic standpoint, not a visceral/reactionary one.

edit: spelling mistakes due to my shitty keyboard

@Centurion

Of course it was hard to say whether a band would become a Dark Wave or a Punk band when they made their first records in the early 80ies. We had an old Junkey-DJ who flew once or twice per month to London to find some new stuff. But their was a big difference between Punk and what we simply called Wave at that time. Punk was very violent and they wasted their clubs. No tables or chairs and a bad PA because the sound system was destroyed as well once or twice a year. It was impossible to dance with them, because Pogo means to barge against each other permanently. No Wave was a part of the alternative scene. Beside alternative rock bands there was Reggae, Wave and experimental stuff like Einstürzende Neubauten, Laibach, Bad Religion etc. played in the clubs. It was a different scene. But I can't say whether it was equal in England. Anyway the British gothics could not fight, it would have wasted their extravagant outfits. All in all their might be a little more violence in English clubs.

It's the same with Black-, Doom- or Death metal. They have their own DJs and their own areas. I like to pass over there for a song or two, but they are not so consequently dressed in black and it is a total different feeling. We once had a Sylvester Party with the metal scene in a small club. It was funny. Half an our Metal and half an hour Gothic. I would say the connection between Doom/Death and Gothic is definitely not more intensive as with the Metal Scene. Their Music is more acceptable for many Gothics and we share some bands and influences. Subway to Sally for example or In Extremo, Tanzwut and other medieval bands.

Of course my experience is restricted onto one region in Germany. I'm sure the scene is different in other parts of the world.