Granted, the MB have some moderates, amongst their ranks, along with the bulk of extremists involved in running this organization. However, moderate and extremist elements in the MB all have one thing in common: rather than allowing people to practice religion within the context of community, they want to inject religion into all areas of life, through the obtaining of political power, thus the term "political Islam."
Most of the Islamist groups in Sunni Islam sprang out of the MB and figures like Sayyd Qutb. These include Takfir, Jammat Islammya, etc. Their activities: persecuting religious minorities and Muslims they consider heretical, harassing people for breaking the various laws of Islam, killing tourists, politicians, like Egyptian President, Anwar Sadat (in 1980), etc., have gotten them arrested. Rightfully so, I am sure you would agree.
In fact, it is important to note that the MB has often gotten leniency from the state (when compared how others are treated for similar crimes), since they have many members in high positions of power. They, and their actions, also have the support of many of the Muslim clerics that work at Al-Azhar, the prestigious, connected and powerful Egyptian Islamic university.
So, rather than supporting terrorists, the West needs to encourage and support the secular and moderate elements of this movement, in my opinion.