War has returned to European soil, and it seems that Europeans are not capable, or not willing, to apply the lessons they try to teach in other parts of the planet. The European Union, a winner of the Nobel Peace Prize, put Ukraine in an impossible position when it asked it to choose between a political pact with the EU or a close economic relationship with Russia. Ordinary people in Ukraine have some of the lowest wages in the continent, and face one of the highest levels of political and economic corruption, creating hopelessness among many of them - hence the offer from the EU seemed to many like a golden opportunity to take a first step out of the mire.
The use of violence by both sides in the later stages of the Maidan protests created a precedent, and served as a justification for the use of violence in parts of Ukraine where many people disagree with the country's new political course. Also, the presence of neo-nazis in the new official Ukrainian politics, and the rise of the paramilitary units connected with them, encouraged other Ukrainians - in areas where many feel more attracted to and connected with Russia than with the EU - to consider armed struggle a legitimate method of dealing with conflict.