Because you took your promise you made and your vows to heart.
Yes I have a feeling you just may feel differently about this. Maybe not tomorrow morning, but you may soon. That's why it's so important to give this a little time. A couple of days perhaps before you make any decisions about this. You have just been hit with another bomb.
Only you can decide if/when you're done, you have every right to be angry. I think your smart enough to know not to make any decisions based on that anger.
I'm sorry this is happening, but it may need to come to this in order for him to work through his issues.