I've personally chalked this one up to Dewitt's penchant for writing embellished historical fiction.
I think I agree as to this "Peace and Safety" watchword business. I think it's a reasonable extrapolation, but it needs to be clearly considered to be that.
In earlier years I tended myself to use that phrase a lot and I think I used it frequently at NewEpicurean.com. However I've consciously stopped doing that in recent years, and I am about ready to deprecate it entirely, especially since it doesn't fit well with the "warrior Epicurean" approach that I think is more accurate. It might also possibly be a phrase that the Christians were using in a deprecating manner, which is an aspect that DeWitt might not have approved of in the way he described it.
All in all I think this is one of the examples that I would most frequently cite as a point of departure between me and DeWitt.
I don't think it's totally harmful, and I can see the strong attraction of wanting to give people who are familiar with Christianity a reason to be interested in Epicurus, but I do think this is overplayed.
I haven't pulled out DeWitt to check the reference before writing this, but I definitely agree with this:
This might be one of those instances unless someone knows where there is mention of Peace and Safety as a greeting or motto in the Epicurean texts. I'll happily give a mea culpa.