I may be biased because I clung to a couple of friendships long after I should have abandoned them, but you may have to start considering that the friendship cannot be salvaged.
Regardless, if a friend is unwilling to accept you have differing beliefs, and even resorts to childish insults because of it, you probably ought to really reflect on whether or not this person is a true friend.
Regardless, if a friend is unwilling to accept you have differing beliefs, and even resorts to childish insults because of it, you probably ought to really reflect on whether or not this person is a true friend.