First there are different varieties of freemasonry, and, I only have an outsider’s knowledge. The major variety in the US are those lodges recognized by the United Grand Lodge of England. In them the initial three degrees (third degree is for master mason) only require a belief in God (and that one be male and “freeborn”) and no one need go beyond them to be a mason in good standing belonging to a lodge (blue/craft). Once a mason one can but certainly need not do Scottish Rite or York Rite and those are very Christian; they may even have been a reaction to the ordinary lodge emphasizing fellowship across denominational or religious boundaries. Freemasonry certainly has no problem with Christians (or Jews or Muslims or anyone but atheists) joining; however, various groups oppose their members belonging. Reasons include
- Sometimes freemasons have discriminated in favor of fellow freemasons in employment or business or policing.
- They do cut across religious boundaries which has sometimes been seen as a threat (note they first appeared around 1700 [despite claims of a long history] in Britain at a time when different religious groups tended to be insular).
- They are officially secretive about their rites which leads to rumor.
- They have at times been centers of radicalism (think of the number of American revolutionaries who were freemasons). This does not hold true in modern US where some lodges still do not accept African American men as candidates (there is in fact a parallel structure of lodges, Prince Hall, for African American men). Politics is also usually forbidden as a discussion topic.
Note lodges associated with the Grand Orient de France (which is not recognized by the United Grand Lodge of England) have somewhat different requirements. They do not require belief in God and may admit women. They also may allow discussion of politics.