Two different situations. Their not really at all alike.
Nas was straight shytTING on nikkas. Whether you agreed with his assessment or not that's what he was doing. Nas was at a point where he was absolutely disgusted with the rap game and how it wasn't even being run by the MC's but the labels and corporations, he took umbrage at Hot 97 hypocritically refusing to allow him to perform Ether and hang the Jay-Z doll and went to Power 105 with the express intent of calling out names and making the most insulting comments as possible.
Kendrick's verse was a battle cry of competition. This wasn't personal nor was it intended to truly end careers. Nas was out to end nikkas careers that day. Kendrick was out to make a statement that he was the best and threw the gauntlet down for all challengers to dare him in a musical forum. He didn't call anybody's album "Wack" he didn't proclaim that he single handedly made one of the most successful rap crews of that era "scatter like roaches" and he didn't call any labels " evil empires". He RAPPED about wanting to be the best, made his case, stated whom he felt his Competiton was (which is in effect showing respect for their skills) and basically told them "it's all love but its on" Nas wasn't showing love to NO nikkas that day...
I love Kendrick's verse and what's it doing to and for the Hip Hop landscape right now. I honestly feel that besides Lupe Fiasco, NO MC of the newer generation is touching him. But let's not make his statement into something it's not. This isn't about beef or going to REAL war like Nas and Jay-Z did or the Bravehearts and Dip Set did. This is about bringing legitimate Competiton back to the forefront of the lyrics in manner that a lot of NY MC's were during the early 90's. Biggie Vs. Nas, Biggie Vs. Jeru The Damaja, Biggie Vs. Raekwon and Ghostface. Those were battles that were fought to prove who the best was, born out of pure Competiton and respect for the adversary. THAT'S what K.Dot's message is centered around