Science fiction in Slaughterhouse Five

Recently we have gotten into the debate about the presence of science fiction in Slaughterhouse Five. The focus at the beginning of this debate dealt with whether the science fiction aspects takes away from the seriousness of the novel.
To answer this I believe it is important to evaluate how humor is used in the novel. Throughout the novel there have been humorous bits scattered about, the form of the Trafalmadorians comes to my mind in particular, clearly comparing an alien to a "plumber's helper" is supposed to be taken somewhat lightly, the aliens are the complete opposite of the typical alien image as they are basically one eyed walking hands. So yes this may take away from the seriousness of the novel because of the way humor is added in the science fiction parts of the novel. It could be said that the majority of the humor in he book comes from the science fiction portions of the novel and I think this may have been done on purpose. The science fiction sections of the novel have been the sections that have provided us with the most complex ideas. In order to not weigh down the reader too much I believe Vonnegut gives us these humors bits so that our understanding of these ideas of time, human insignificance, etc don't lead the reader down a path that ends with them jumping to extremely negative conclusions, instead the humor creates some balance that creates a neutral context for the reader when they attempt to make sense of these complex ideas.
 I think yes, the humor may take away some of the seriousness, but it is also essential to our interpretation of concepts in the novel.