Not a fan of Brennan, but in all fairness he's quoting a fan, not saying Karlsson was a garbage pick (of course he has his doubts). The season ticket holder said "That's a garbage pick. They could have had him in the second round." and Brennan responds "Thing is, we really don't know how good Karlsson can and will be.". Brennan said Karlsson was going to be good. How good? Well, it was hard to tell. He never said Karlsson was a garbage pick.
Also, if we drafted another 5'10" 150 pound guy in the next first round I'm sure there will be a bunch of people enraged with Murray for picking such a small player and another bunch thrilled that it could be the next potential Karlsson. No body could have said on his draft day Karlsson would be one of the best if not the best.