Excellent advice given.
I agree, taking down their stuff hurts YOUR witness.
Remember this, the God who created the Universe can make sure the tracts get into the right hands. Also, many publishers have created good tracts specifically for atheists. Grace & Truth has some and are very affordable.
I hand out Bibles & Scripture booklets in bags of candy. I figure maybe half of the "Jesus" actually stays with the original recipient. The rest moves on, into the RIGHT hands. One of my guys had a passenger passing out from low blood sugar, after I had gotten out. He gave her the bag of candy.

Helped her twice, physically, and spiritually.
Always be ready to preach the Gospel, in and out of season. Pray for everyone; remember, prayer is one of the most effective weapons we have in the arsenal.
Especially pray for those who come against you, and the future recipients of tracts & testimony.
I have complete strangers walking up to me now and asking for Bibles, even without the sign!
