While we're on the subject of why frugality is, for many of us, not at odds with Christian faith:
What do you think is a bigger problem in the world today: a few thrift-shopping moms with a gift for decorating and crafts, or the mound of consumer debt out there? How about fragmented families, disconnected parents and children who don't have time to have a life together outside of work, school, and everything that you have to get chauffeured to afterwards? If part of our ministry as Christians is to support family life, then why whack at people who are doing their best to nurture their families and create gracious, friendly homes? I'd say that the dearth of families and homes like that in North America is a much bigger problem than whether or not we bought the book we're reading together for twenty dollars or twenty cents.
(And on another side note: although I do love to thrift-shop books, I will buy new books too. I happily bought a set of the Little House Martha books from a homeschool vendor because I know at least two families--the vendor's and the author's--benefitted by that purchase--besides ours.)