I was reading a little bit last night about Dorothy Day and the Catholic Worker movement.
I always feel myself at a bit of a disadvantage dealing with some of the more edgy proponents of Church social teaching, in that in many cases I think their political and economic (though not their spiritual) ideas are faulty. So while I think that the Catholic Worker movement has done a lot of good in promoting the kind of radical support for the poor that saints like Saint Francis also performed, I also think that their pacifism and many of their economic ideas are incorrect, and perhaps misguided.
What I came around to is that there are many activities which can lead to great holiness, which, if made the center of one's spirituality can lead one astray. The perfect example is the way in which (within a generation of St. Francis' death) his poverty-centered spirituality gave birth not only to the thriving Franciscan orders which have helped the Church down to this current day, but also the various heretical groups known as the Fraticelli. Francis himself, and countless followers, did great things for God through their vows of poverty. But for those followers who came to believe that total poverty was the only means of holiness, the same spirituality became the path to heresy.
Similarly, someone who is a sworn non-combatant (even in an eminently just war) can do great things for God. But it seems that many people easily move from their own self sacrifice in assuming a life of poverty, or non combatant status to asserting that property ownership or just war are in fact wrong, taking their own spirituality and making it an overarching norm for all Christian salvation.
The temptation exists on the 'traditionalist' side as well, where those who rightly love the Tridentine Rite set that good up as the only good and condemn all other forms of worship as corrupt.
The key, I suppose, is to remember at all times through careful reflection and submission to the Church the difference between ones own spirituality (however acceptable to the Church) and elements of the magisterium to which all the faithful much in good conscience hold. No easy task, but Christ did not only call us to do the easy things.