Overreacting and confirming their prejudices.
That said, is six years in prison for taking part in a poorly attended demonstration which was designed to cause outrage an appropriate sentence? It seems ridiculously harsh, especially when we remember that Abu Hamza, who preached hatred and was involved in the radicalisation of a number of young Muslim men over a period taking in the late 90s and early 00s, was only sentenced to 7 years. Is such a sentence likely to do anything other than further exacerbate the pathological hatred which these men already have for this country, and also influence others already sympathetic to their cause? A sentence of two or three years would have been more than adequate, showing that such displays are completely unacceptable and will be punished harshly, but not overreacted to.