Should brokers offer Negative Balance Protection or not?

Yes, Forex market is uncertain. No one can be 100% sure about either market will be upward or downward. Every trade knows chance of loss as well as profit is same. That's why, i think negative balance protection is necessary because if market rapidly goes against your trade due to negative balance protection will help you.
What you say all best Forex broker offer it or not?

Mandatory.

B-book clients should have negative balance protection because when b-book clients go into the negative, the broker hasn't actually lost any money. They just create this fake debt and demand that you pay them back. This is on top of your deposit they pocketed from when you lost your trade

agree with you