'Could I be fired if I denied the existence of God and pointed out to a Christian co-worker that their beliefs were nonsense. I get that would probably be me being a dick, but that shouldn’t be a sackable offence.'
Thing is, this is worse than that - it isn't about anything Maya did or said in the office, or to a colleague. It's about calm, thoughtful, reasoned tweets made on her own social media in her own time.
It would be like being fired for saying in general, in your own time, that you don't believe in God, rather than to a Christian coworker.