One study is not intended to be totally convincing. Rather, what it does is provide two primary functions: 1) support a claim through documentation, and 2) substantiate that claim goes beyond just spurious information.
Since it is a study, there is some scientific process involved and in order to disprove it you then must provide information that counters its validity or show where it may not be applicable to the topic. A study can additionally provide information and insight on a particular item or category paving the way to further investigation.
Believe it or not, even an opinion can be valid support of a claim if it comes from someone who is a professional or has experience within a particular area. Not everything needs to require a scientific study to be valid or believable. Remember, the first rule of a scientific model is observation.
I've learned that when someone doesn't want to accept a claim they will find a way to invalidate it where it makes sense or not. When that happens, its best to just leave the discussion and move on to the next topic.