On of the main reasons you will find some atheists seem to have a militant attitude is that many religious apologists attempt to co-opt ideas that have developed in Western democracies.  I would attribute the 'natural rights' to the magna carta rather than the church.  And while some tenets of the New Testament have had a positive influence (a significant positive influence), there are many that have been negative and most Christian churches have been very slow to recognize the universality of the ideas attributed to Christ.
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I enjoy and appreciate the Christmas season for the positive aspects it brings out in general, the goodwill, the friends and family, the feasting.  But it has more to do with the celebrations that predated Christmas and were co-opted by Christianity than anything Christians have done