FWIW, the swearing in with a Bible is nothing but a ceremonial photo op.  The real swearing in takes place at a different time with a simple right hand raised, usually with all of the senators (or whatever) together.  If someone refused that sham, they would be just as leagally sworn into office.  Though I believe in the Bible I would not want someone who was opposed to it raising their hand and lying about it.  The time for that discussion is before the election.