The pharisees condemned Christ because they knew he was referring to Daniel 7:13-14 when he said they would see him coming in the clouds. In other words, they condemned him for claiming to be the fulfillment of that prophecy. Has nothing to do with your imaginary modalism thing
Not that you need to answer these questions here, but ponder on them a little bit. So it is that the Christian religion is held up by two pillars; the trinity doctrine and the Gospel of Jesus, which this religion is certainty of salvation. The Oneness modalist cult has to deny both these pillars and therefore is firmly outside of the religion because of the pernicion of their heresy and the consequences of that are certainty of damnation. Due to the length of eternity it's worth sparing a little time now to think about.