Followers of Jesus Christ are called Christians. Claiming to be a Christian when you are not is taking the Lord’s name in vain. This is being a hypocrite and all hypocrites will go into the lake of fire with the unprofitable servants.
Exodus 20:7, “Thou shalt not take the name of the Lord thy God in vain; for the Lord will not hold him guiltless that taketh his name in vain.”
Matthew 24:50-51: (The unprofitable servant) “The lord of that servant shall come in a day when he looketh not for him, and in an hour that he is not aware of, And shall cut him asunder, and appoint him his portion with the hypocrites: there shall be weeping and gnashing of teeth.”
Swearing in the name of the Lord is also taking His name in vain.