The paper presumes that social media is an environment where local and small events may escalate into bigger and even global ones in a very short period of time. This is because social media offers opportunities for discussion of shared interest in way which cannot be controlled: everything that can be exposed will be exposed - for all intents and purposes. This possibility has also changed the landscape of discussions of controversial issue, such as foreign and security policy. Compared to traditional mass media, social media enable disclosing opinions without censorship. Nowadays people have access to online discussions, blogs and even websites entirely devoted to sharing negative information. It has been seen that, during crisis situations social media has become a major way of affecting people's opinions. Consequently we are witnessing the rise of trolls - individual who shares inflammatory, extraneous or off-topic messages in social media, with the primary intent of provoking readers into an emotional response or of otherwise disrupting normal on-topic discussion. Based on the lack of censorship, on the one hand, and trolling behavior, on the other, the paper aims to understand the rise and diffusion of extreme opinions in Twitter. This is a case study paper, where the analysed case is Twitter messages on Ukrainian crisis during 2014 written in Finnish language. The aim is to utilize sentiment analysis for the automatic detection of trolling behavior. Sentiment analysis provides tools for strategic communications for the automatic analysis of social media discussions and to recognize opportunities for participating in the discussion at the most effective stage.