Non-Christian Easter rituals
This ritual has the appearance of making an argument -- #many Easter traditions have a pagan origin, therefore Christianity's righteousness is somehow compromised.# But it doesn't really function as an argument. These things are mostly said not to Christians, but to other non-Christians -- e.g. in this Pandagon thread. And I doubt many Christians who are otherwise secure in their faith are particularly troubled by these historical facts (certainly I wasn't). Either they already reject all the aspects of Easter that aren't found in the Bible (including, sometimes, the very idea of an Easter celebration), or they don't see enriching their holiday with elements from another tradition as necessarily threatening the remembrance of Jesus' resurrection (coloring eggs can be just a fun thing to do, not an act of worship of Oestre).
Instead, pointing out the pagan roots of Easter functions as a ritual for affirming non-Christian identity and solidarity (a quite useful function, I might add, given the dominance of our society by Christians). It's a way of reminding everyone in the group of non-Christians' superior critical thinking skills (which are held to be the basis of non-Christianness, much like faith is the basis of Christianity), and holding up Christianity -- particularly Christianity as unthinkingly practiced by the masses -- as ridiculous to anyone who knows some historical facts. Indeed, there's an interesting parallel in that both Christian and non-Christian Easter celebrations are about affirming the group's knowledge of a hidden truth that they want to spread.
*I use the term "non-Christian" here for lack of a better one -- this ritual is not particularly common among devout practitioners of Islam, Hinduism, etc., but neither is it exclusive to people who entirely reject religion. I've even seen it among a few rationalist liberal Christians.