By now, you have almost certainly heard about the churches in Bend, OR, that were vandalized. Some moron saw fit to spray paint "Praise the FSM" on two churches. This cowardly act accomplished nothing and has been rightly condemned by the atheist blogosphere. There are many effective ways to send a message to local churches or members of one's community; vandalism is not one of them.
In my opinion, the best argument against this sort of behavior is that we do not like it when Christians do it to us. Atheists have been victimized by Christian vandals again and again. That does not make it right for us to do it; in fact, our experience of being on the receiving end should remind us what it feels like and discourage us from lowering ourselves to their level.
The least persuasive argument against church vandalism I've heard is that it makes us (i.e., atheists) look bad. Um...we already look bad. We're already hated. Study after study shows that we are the least trusted and most despised minority in America. And we're not hated for what we do as much as for the fact that we exist at all. So I don't see this as a compelling argument for much of anything.
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