Why is God's grace offensive to some?

The offense of the gospel stems from the stark contrast between man's idea of fairness and God's sovereign grace. Many struggle with the notion that God unilaterally chooses whom to save, viewing it as unjust. However, Romans 9:15-16 explains that God's mercy is not based on human desire or effort, but solely on His will. People find this challenging because it forces them to confront their inability to contribute anything to their salvation and the fact that they cannot dictate God's actions. This realization can be deeply unsettling.