Does not responding to insults and curses indicate a weak personality, and what is the best way to preserve one's dignity, and how did the righteous predecessors deal with curses and insults?

If a Muslim is subjected to oppression, it is legislated for him to strive to demonstrate his ability to triumph, and then to forgive after gaining power. This is what the Salaf used to do, for a Muslim should not abase himself before the wicked. Praiseworthy forgiveness is forgiveness after gaining power, not when one is helpless, for forgiveness when helpless is humiliation and disgrace. As for cursing religion and the like, there is no forgiveness for it; rather, justice must be exacted, because it is a right of Allah Almighty, and a Muslim must exact Allah's rights as much as possible.