In answer to your question I am not a very good Christian to ask, as I believe I am still learning the theological parts. When I became a Christian I did't understand either, but through other Christians asserting it and reading the new testament, especially Paul (Awesome guy) it is clear that through Jesus name we can be forgiven for sins. If he was not God, then perhaps we can't be forgiven for sins in his name (which is why Jesus was persecuted). Without forgiveness of sins then we cannot be reborn, so it really puts a downer on being a christian. Also just thinking out loud if Jesus was not God then he was some kind of minor God, which departs from the monotheistic Judaism.
Ephesians 1:7 - In him we have redemption through his blood, the forgiveness of sins, in accordance with the riches of God's grace.
