You are capable of destroying the Rākṣasas very easily (I admit)—but Rama's fame shall then be souled if do you bring about their destruction.
कामं त्वमपि पर्याप्तो निहन्तुं सर्वराक्षसान्। राघवस्य यशो हीयेत् त्वया शस्तैस्तु राक्षसैः॥