It's because information can be interpreted many ways and if you seek to disprove your own opinions you'll quickly find you don't believe in much of anything.
If you were talking about science then you might be right, there should be clear conclusions from any given information and if not there must be some other hypothesis. But if you require absolute proof before forming a reasonable conclusion then we would never have a weather forecast. And a subject like politics doesn't necessarily have any universal right answers, the more complicated the issue the more likely a particular statistic can be misleading. I'm not saying ignore all evidence of course, but you can ignore some doubt, particularly when there are multiple ways to look at things.
Obfuscation : The politician's friend.