The world in general is a legitimate and respectable place for physicists to publish preprints, but you still shouldn't believe everything you hear in the world. I think that's the point. It's not that arxiv sucks, but that it doesn't lend any credibility to the things published there, so we need to be skeptical. For those of us who are not the author's peers, taking non-peer reviewed work as anything more than speculation is likely to lead to false beliefs.