If Jesus were not God the Son, then we have two immediate problems. The first is that His sacrifice for "all mankind" is simply not enough to pay the price of all our sin.
The second problem is that He had promised salvation to His listeners. If He knew He was not the Saviour, then He was no more than a conman - an out and out deceiver.
No surprise then that it is a very common tactic of His enemies to portray Jesus as merely being "a good man" with the Sermon on The Mount adduced as evidence.
Sorry. It won't wash. Either He is God the Son; our real and present Saviour OR He was a very "bad" man. No compromises are possible.
