Deism and Christianity can exist in harmony with each other. It is about respect. They need to respect each other and respect their differences in beliefs. I think a better question would be, will Deism and Christianity live in harmony with each other? They need to decide if they want to live in harmony with each other.
Deism supports the notion that science and reason are enough to support the existence of a divine creator or God. Christianity purports Jesus is our lord and savior and the only way to heaven is through Him. Tenets of both faiths create moral codes that deserve to be looked at by contemporary people as valid ways of behaving. Deism was followed by many of America's Founding Fathers. Since then, Catholicism and Protestant Christianity have become mainstream religions in the United States.
Christianity relies solely on belief and faith. It teaches that if you have faith in beliefs, then will know the truth. Deism, on the other hand, teaches that it's only possible to find the truth through logical reasoning and observation. Christianity also relies on groups for survival, which is demonstrated through the attendance of church. Deism, however, promotes individual thought and pursuance.
Deism and Christianity cannot exist in harmony with each other because they are contradictory systems of though. Christianity demands that its followers swear that Jesus Christ is the one true God. Deists, on the other hand, believe in a much less precise definition of god. These two beliefs have fundamental differences.
I don't believe that deism can coexist with Christianity. This is because pretty much no other religion can coexist with Christianity. Most Christians are sure they are right and all other beliefs are wrong. They look to convert everyone, not allow them to just coexist. Deism can probably coexist with Christianity though.