You underestimate how far right the US is.
And the peace treaty means nothing to all the drone strikes/bombings and the war in Yemen. Not to mention his time in the Senate before that, does the Iraq war ring any bells?
You can talk about how much Biden is the lesser evil, I won't disagree. But denying his warmongering past? That is just straight up dem propaganda. Biden was known as the most conservative/right-wing dem in the senate for a reason.