There is lots of historical evidence for the fact that Jesus actually lived on this earth. Historians may not acknowledge that Jesus was God; however, His humanity is undeniable.
Dear friends, do not believe everyone who claims to speak by the Spirit. You must test them to see if the spirit they have comes from God. For there are many false prophets in the world.2 This is how we know if they have the Spirit of God: If a person claiming to be a prophet acknowledges that Jesus Christ came in a real body, that person has the Spirit of God. 3 But if someone claims to be a prophet and does not acknowledge the truth about Jesus, that person is not from God. Such a person has the spirit of the Antichrist, which you heard is coming into the world and indeed is already here. (1 John 4:1-3, NLT)
Jesus is both God and man. To deny either rejects the truth of who He is. Jesus had to have an earth suit in order to legally access the authority that God gave to man (which Satan stole from Adam). However, in order to pay for the sins of the WHOLE world, He also needed to have a life worth all the souls that ever lived - as God He did.
The majority of the world does not necessarily struggle to accept that Jesus existed, but they definitely struggle accepting His divinity. On the other hand, the above scripture speaks about false prophets and the spirit of the antichrist. This Antichrist spirit is an acknowledgment of Jesus' divinity, but a rejection of His humanity. To say that Jesus did not come in the flesh is to reject the very power of God for salvation - the gospel that Jesus paid the price for sin by dying on a cross and that He rose again the third day.
To say that Jesus did not have a physical body is to say that He did not die. And if He didn't die, then He couldn't have risen and nobody is saved. That is the Spirit of the Antichrist, which is of course a lie.