I'm not talking about being seriously offended to the point of it seriously affecting your emotional state for anything more than a few minutes, but if someone really loves DT or KM, I don't think you should expect them to enjoy hearing "This really sucks... They should fire the organ player." And perhaps if they perceive it as an insult of their musical tastes, which isn't, like, a totally unreasonable interpretation, that could also offend them.
Honestly, Mike Portnoy being offended or not being offended by something should really have nothing to do with whether someone not named Mike Portnoy is or is not offended by the same thing.