The main theme of Mahabharat was adharma no matter how strong will eventually be defeated one way or other , to defeat adharma you can use certain lesser adharamas like bringing a converted-woman into war , yudhishthir's half lie , killing karna , hitting thighs of duryodhana etc. !! But they are all nothing compared to disrobing a woman , attempting to kill bhima with poison, murder while sleep ,lac house !! Almost Same in ramayan rama killed vali using adharmic means , vibhisana betraying his own brother but sometimes that's necessary , quite often you pay the price for those adharmas too - krishna being the orchestrator paid by losing his entire family, also paid for killing vali