Are all Muslims terrorists? The answer to this question is not simple. The answer is no but, in effect, yes because of STS. See Terrorism: STS Syndrome & The Hidden Terrorist Threat.
Those who grow up in a terrorism environment, like Muslims, develop STS (Sustained Terror Syndrome). The chief symptom of STS is desensitization to violence. This explains why M-victims (Muslim-on-Muslim victims) can be as dangerous as M-terrorists; that is, they have given up the ability to fight M-terrorists and will submit rather than defend themselves or you.
Therefore, you should not count on M-victims (Muslim-on-Muslim victims) to come to your aid in a terrorist situation.
Therefore, in effect, not actually, all Muslims are terrorists. While we may easily forgive the M-victims, we must always remember that they are as much a threat, because of their STS, as terrorists.