Why did loyalists withdraw from the second continental congress in june 1776?

Because they were anti-independence. That meeting was to write the Declaration of Independence.  

Communicating with the dead was common, it wasn’t seen as bizarre or weird,” explains murch. “it’s hard to imagine that now, we look at that and think, ‘why are you opening the gates of hell? ’

The second , larger puritan colony of massachusetts bay was conceived as a "city upon a hill". but it also struggled with internal turmoil like the salem witch trials and external conflicts like king philip's (metacom's) war.