No, I don't believe the console command works for reducing militancy. To get around this I ended up scripting an event in. I've added the event below, but note this resets militancy back to zero. If you want a different level then you will have to adjust accordingly.
SelectFaction = $RUM
StartEvent = evt_nam_RUM_MilitancyReset1860|1|0|NULL|NULL|NULL|NULL
MinDate = 1864/01/01
ChgPopContentEx = 100;100;100;100;100;100;ALL
ChgPopMilitancyEx = -100;-100;-100;-100;-100;-100;ALL
Note that the effects won't show until the next round of tax hits on the population, and if a region is already in serious unrest the levels of unrest (i.e. strikes, etc.) will only gradually reduce in intensity. Also, the levels of contentment and militancy will automatically begin changing again according to the situation in your game, so even though militancy may reduce to zero in one province it will begin climbing again as normal.
Looking through the event files within the game structure gives a good idea as to what can be edited and added through events. The best place to add in a new event is the "Plugin_...." files under the events folder. In any case, wherever a new event is filed just ensure that event file is included as one listed in the appropriate campaign script file in the events folder, named for example 1850 GC, 1870 FPW, etc.