He said things like "I am the way, the truth, the life. No one comes to the father but through me." "The father and I are one." "Upon this rock I will build my church." When he was killed, it was clear that he wasn't building anything.
So how did the early church actually get started after he died? Anyone who denies the resurrection would have to answer this question and the answer can't be "the same way all of the other religions did it". His message simply doesn't allow for that. Did twelve guys make up a story about the resurrection and people all over Judea who wanted Jesus dead and/or watched him die suddenly buy it and hop on the bandwagon? Possible, yes... but not really probable. Bringing the dead back to life would have sounded just as crazy back then as it does today, right?
Or... did people really see a dead man walking?