"I'm sure these churches are essentially '501C-3 corporations' in which they receive numerous IRS granted tax benefits in exchange for 'compliance' with federal/state laws"
Bingo! - we have a winner!
Which is why God said
Be ye not unequally yoked together with unbelievers: for what fellowship hath righteousness with unrighteousness? and what communion hath light with darkness? And what concord hath Christ with Belial? or what part hath he that believeth with an infidel?.......
Wherefore come out from among them, and be ye separate, saith the Lord,
2Cor 6
However the prohibition against political activism does not apply to churches with a predominantly black membership. Church sanction voter candidate cards, Open endorsements of candidates, and any other "no no" are all permitted if you have the right skin pigment and you are voting for the left.