I quickly looked through the thread for any attempt to define 'religion of peace' - and couldn't find one. If I overlooked it, feel free to direct me to it. Because having a proper definition really seems like the place to start.
I did some googling, and so far as I can tell, the description of islam as a 'religion of peace' originated after September 11, 2001. This would imply that the idea of islam as a 'religion of peace' is not something necessarily supported in islamic texts. It's true that there are many references to peace in those texts, but there are also many references to war. Islam101
argues that these instances don't negate the idea of islam as a religion of peace because "Such verses relate in a restricted sense, to those who have unilaterally attacked the Muslims . .. [and] do not convey the general command of Islam."
Well, if peace is the general command, but there are exceptions where violence is permitted, to what extent can you say it's a religion of peace? I suppose a comparison could be drawn between this idea, and pacifism and nonviolence; it's possible, for instance, to be opposed to violence in a general sense, but not be opposed to violence in emergencies and self-defense.However
, there are also religions which seem to be even more opposed to violence, in all forms. Jainism is often cited as the most extreme example of this, in that violence is forbidden not only against people, but the most minute creatures - and 'violence' is not limited to physical violence. I admit I don't know much about jainism - or related belief systems - but from what I could find, self-defense is, or can be permissible. But even in those cases, it appears to encourage limiting violence. Jainism certainly does not appear to encourage you to "Kill them wherever you find them".
Now, this doesn't really get anyone any closer to defining the term 'religion of peace' - but I'm not even sure how useful that would be. It seems like an empty concept no matter how you look at it.
Of course, in a practical sense, most religions are peaceful - including islam. Because, in the end, people tend to be equally decent or indecent regardless of what their religious affiliation is. I think you have to allow for the possibility that people are moved to violence because of religion. What we see in Iraq and Syria today, however, probably has no more and no less to do with religion, than any other example of religious violence in history. And, in the end, you'd probably understand more about the violence in that region today if you studied the effects of armed conflict on psychology and politics, than you would studying religion.