What is the academic approach when the supervisor attacks student's religion?
No matter what the advisor's beliefs are, it's not OK to discuss a student's differing beliefs AND criticize them. It's the criticism that takes this from honest exchange of views into a more dangerous territory: your advisor is in a power relationship with you by definition and it's impossible to have a discussion "as equals" while this relationship is active. 

If you think that the relationship and his continuing advising would be beneficial to your career, then you might try to have a chat with him where you indicate that these topics need to stay out of bounds. And I'd erect a high bar for "beneficial". 

But if your assessment of value does not cross that high bar, then I'd follow JeffE's advice and run.