There needs to be a plumline to compare morals to. How can one be moral in a relativistic society since most people define a moral by their own standard. Some people think that certain things are okay and that difference causes problem to most people. Using Christianity and the bible sets one universal law for us to follow
In order to even talk about what is or isn't moral there has to be "good" and "evil", a moral law. In order for there to be morality there must be a transcendent moral law giver. The reason this is necessary is because all questions of morality are either raised by a person or about a person, so something above a "person" has to give this law. Like I mention in order to talk morality you have to accept evil and good. For there to be evil there has to be good, for there to be good there must be a moral law giver. The idea of morality presupposes God. Morality is borrowed from the Christian world view. So ya I'd say you need Christianity to debate morality, though I would rephrase the question slightly. Maybe "Is the Christian worldview necessary to have morality in the world?".
We all like to say we are good people with morals, loyalty and trust. The fact is we also all know that is not always true. Sometimes I believe the mention of churches, religions and Christianity is used to create an automatic God-like, therefore right image. Once we involve Christianity in debates, we then need to access which type of Christianity is needed. The religions left out will feel bias because they were not chosen.
The idea is, morality is normally taught at home, school and maybe church. If you did not start learning what it means at an early age, being Christian certainly is not going to teach you differently than what you learned at home. You are a product of your parents and live as such. Everyone has a pretty specific meaning of morality in mind, we do not need to debate what it is, or have it deemed right or wrong by Christians.
If you were going to debate Christian morality, then yes it would be needed. However, the question seems to assume that Christianity is the only form of morality out there. Even some of the more alternative pagan religions still have a hard code of ethics to go good by others and your community.
Morality is not entirely a man constructed idea, but it does not require religion. Evolutionary, mortality is a set of rules which help the species to survive. Animals demonstrate their own versions of morality; they do not tend to kill each other for no reason. Ironically, no animals are Christian.
Moral arguments were conducted long before Christianity was formed. Just look at some of the Greek literature that still exists. The works are rife with arguments for and against certain ways of thinking and moralities. To believe that Christianity is the only source of morality is ignorant, even as a Christian. Not to mention that much of the morality of Christians developed from Judaism.