See I believe hate tends to flourish in large groups, and a deep inner-savageness emerges within us (Some william golding right there!). Lets take your typical view of, say Nazi ideology.
Although there was many factors, say the current German economy, Hitler manged to identify this hatred of the current Wiemar Republic government, social impacts and the tension between political affects. Its human nature to mimic or respond to emotional distress such as this, and many people began to mimic this hate, without any logical justification nor reasoning, but rather excuses, for example on the jews. No concrete evidence for the wrong they did, and as also a minority in Germany, yet such atrocities were committed against them. Again this is because i believe hate flourishes in groups, to a point where sub-consciously or without rational thinking, the mind demands hate for pleasure. This is supported by Freud's theory of the 'id' where the sub-conscious will react instantly in order to gain pleasure rather then rationally, regardless of consequences.
I feel like this is reflected in modern-day society. For example say President Trump has identified and targeted all the hate that has been building up against Muslims, due to atrocities such as 9/11 etc. and used that for his own political advantage. This increased the flames of hatred, which is why Hate crimes against Muslims soared, and many people seem to mimic this wrongful behaviour regardless of reasoning.