Again, with tongue somewhat in cheek, it might be asked why the promotion of peace and love apparently precludes intolerance of everything except Christian intolerance.
More seriously, it seems as though the notion of tolerance is perhaps misunderstood when it is referenced in contexts like these. As far as I understand it, the act of tolerating a particular behavior or belief necessarily involves allowing, or, one might say, "putting up with" the behavior or belief even though one disagrees with it. If this is the definition, I fail to see how Christians are not tolerant, given that they put up with things to which they are opposed all the time. But if tolerance instead is supposed to mean the approval or endorsement of a behavior, then no one is tolerant of everything. Indeed, if Christianity is true, then tolerance of things non-Christian in that sense would promote neither peace nor love.
You may also be interested in reading The Myth of Tolerance