The implication of this God's promise to not again destroy all living creatures as he had done is there has never been a global destruction since God made that promise to himself. I think that is what a believer would say.
But what is exactly your objection to this God who wants to be loving and forgiving?
Imagine you live in a country run by a tyrant who arbitrarily kills his subjects. Then one day, when this tyrant is doing his powerwalk around the royal park, you spit roast some fatty meat in the park where he is going to pass by. When he is getting close to you, he can smell the pleasing aroma of your roast which makes him hungry. You offer him to have some of roast. He is delighted and says to you: DBT, your kindness in offering me this piece of meat has made me realise that from now on I have to be kind and loving to all subjects of mine.
What would you say to him? Would you say: No, you can't, Sire. You have to be punished first for the cruelty you have committed? I am sure you wouldn't because you that tyrant is above the Law (just like the English monarch!).
