Sure it sounds plausible because it fits the world view of most here. The whole reason we have the scientific method and statistics is to remove personal bias that from the equation because if you don't you get nonscientific crap. The process only works if you use it every time. You can't just say "meh, good enough" because you find the results plausible. This study did not attempt to do a very extensive job controlling for other variables and likewise we can't just accept the conclusion at face value because we find it reasonable, more work needs to be done.